System for controlling exterior vehicle lights

ABSTRACT

A system and method of automatically controlling exterior vehicle lights includes an image sensor and a controller to generate control signals. The control signals are derived based on information obtained from the image sensor as well as other detected parameters pertaining to the detected light source(s), the vehicle having the inventive control system, and the ambient environment. The control circuit may simply turn certain exterior lights on or off, or change the brightness, aim, focus, etc. to produce various beam patterns that maximize the illuminated area in front of the vehicle without causing excessive glare in the eyes of other drivers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 09/800,460 filed Mar. 5, 2001, entitled SYSTEM FOR CONTROLLINGEXTERIOR VEHICLE LIGHTS by Joseph S. Stam et al., now U.S. Pat. No.6,587,573 which is a continuation-in-part of U.S. patent applicationSer. No. 09/528,389 filed Mar. 20, 2000, entitled IMPROVED VEHICLE LAMPCONTROL by Jon H. Bechtel et al., now U.S. Pat. No. 6,611,610 the entiredisclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention pertains to control systems for controlling theexterior lights of a vehicle and components that can be used with such acontrol system.

Modern automotive vehicles include a variety of different lamps toprovide illumination under different operating conditions. Headlamps aretypically controlled to alternately generate low beams and high beams.Low beams provide less illumination and are used at night to illuminatethe forward path when other vehicles are present. High beams outputsignificantly more light and are used to illuminate the vehicle'sforward path when other vehicles are not present. Daytime running lightshave also begun to experience widespread acceptance. In addition, superbright high beams have been proposed for use on fast rural roads. Foulweather lights, such as fog lights, are also commonly used. Otherexterior vehicle lights include tail lights, brake lights,center-mounted stop lights (CHMSLs), turn signals, back-up lights, cargolights, puddle lights, license plate illuminators, etc.

Laws in various countries regulate vehicle illumination, and vehiclemanufacturers must build cars that comply with these regulations. Forexample, regulations set forth by the United States Department ofTransportation (DOT) regulate the light emissions of a vehicle's highbeam headlamps. Various state regulations are used to control the amountof glare experienced by drivers due to preceding vehicles (othervehicles traveling in the same direction) and oncoming vehicles(vehicles traveling in the opposite direction).

Known vehicle high beam headlamp emissions in accordance with the DOTregulations limit the intensity to 40,000 cd at 0°, 10,000 cd at 3°,3250 cd at 6°, 1500 cd at 9°, and 750 cd at 12°. An example of anemission pattern meeting this regulation is illustrated in FIG. 1 ofU.S. Pat. No. 5,837,994, entitled CONTROL SYSTEM TO AUTOMATICALLY DIMVEHICLE HEADLAMPS, issued to Joseph Scott Stam et al. on Nov. 17, 1998,the disclosure of which is incorporated herein by reference. In order toavoid an illuminance of 0.1 foot candles (fc) incident on anothervehicle at these angles, the vehicle high beam headlamps should bedimmed within 700 feet of another vehicle if the vehicles are at anangle of 0°, within 350 feet of another vehicle if the vehicles are at ahorizontal position of 3°, and 200 feet of the other vehicle if theposition of the other vehicle is at an angle of 6° to the longitudinalaxis of the controlled vehicle. It can thus be seen that a precedingvehicle directly in front of the controlled vehicle (i.e., at an angleof 0°) will need to be identified well prior to the controlled vehiclecatching up to the preceding vehicle, although the distance by which thecontrolled vehicle's headlamps must be dimmed for a preceding vehiclecan be somewhat less than for an oncoming vehicle because glare frombehind is usually less disruptive than oncoming glare.

In order to automatically control the vehicle headlamps, variousheadlamp dimmer control systems have been proposed. In order to preventdrivers of other vehicles from being subjected to excessive glarelevels, an automatic headlamp dimmer system must sense both theheadlamps of oncoming vehicles as well as the tail lights of precedingvehicles. Some systems that effectively detect headlamps are unable toadequately detect tail lights. Most prior systems are unable todistinguish nuisance light sources, such as reflectors, street signs,streetlights, house lights, or the like, from light sources that requireheadlight control. Accordingly, these systems are subject to undesirabledimming of the high beams when no other traffic is present and turningon the high beams when other vehicles are present. In addition to theundesirable performance, it is difficult for prior systems to complywith the legal requirements as described above for high beam controlwhile avoiding unnecessary dimming of the vehicle headlamps.

Fog lights are examples of other vehicle lights that are difficult tocontrol automatically. Vehicles are known to include forward andrearward directed fog lights. In Europe, it is known to provide a verybright red or white light on the back of the vehicle, which isilluminated under foggy conditions. The fog lights must be turned ON assoon as the fog reduces visibility by a predetermined amount and mustturn OFF when the fog drops below that density. A reliable method ofautomatically controlling such fog lights has not been available.

Accordingly, there is a need for a more reliable and intelligentautomatic lamp control for a vehicle.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a control system isprovided to control exterior lights of a controlled vehicle. The controlsystem comprises an imaging system configured to image the scene forwardof the controlled vehicle, and a control circuit for processing theimage of the scene obtained from the imaging system and for controllingthe exterior lights to change their beam pattern in response to objectsdetected in the processed scene, the control circuit disables automaticcontrol of the exterior lights in response to activation of the vehiclewindshield wipers.

According to another aspect of the present invention, a control systemis provided to control exterior lights of a controlled vehicle. Thecontrol system comprises an imaging system configured to image the sceneforward of the controlled vehicle, and a control circuit for processingthe image of the scene obtained from the imaging system and forcontrolling the exterior lights to change their beam pattern in responseto objects detected in the processed scene, the control circuit disablesautomatic control of the exterior lights when the vehicle windshielddefroster is operating at full speed.

According to another aspect of the present invention, a control systemis provided to control exterior lights of a controlled vehicle. Thecontrol system comprises an imaging system configured to image the sceneforward of the controlled vehicle, and a control circuit for processingthe image of the scene obtained from the imaging system and forcontrolling the exterior lights to change their beam pattern in responseto objects detected in the processed scene, the control circuit disablesautomatic control of the exterior lights when snow is detected.

According to yet another embodiment, a method of detecting snowfall orfog outside a vehicle is accomplished. The method comprises the stepsof: sensing light levels forward above the vehicle; comparing therelative brightness of the light levels forward and above the vehicle;and determining that it is snowing or foggy when a ratio of the relativebrightness forward of the vehicle to that above the vehicle reaches athreshold.

According to another aspect of the present invention, a control systemis provided to control the headlamps of a vehicle. The control systemcomprises an ambient light sensor for sensing the ambient light outsideof the vehicle, and a control circuit for varying the beam pattern ofdaytime running lamps in response to the ambient light level sensed bythe ambient light sensor.

According to another aspect of the present invention, a control systemis provided to control the brightness of the tail lamps of a vehicle.The control system comprises an ambient light sensor for sensing theambient light outside of the vehicle, and a control circuit for varyingthe brightness of the tail lamps in response to the ambient light levelsensed by the ambient light sensor.

According to yet another aspect of the invention, a headlamp controlsystem is provided for controlling the headlamps of a controlled vehiclethat comprises: an imaging system configured to image the scene forwardof the controlled vehicle; a control circuit coupled to the imagingsystem for identifying and determining the brightness of light sourcesin images obtained from the imaging system and for controlling theheadlamps to vary a beam pattern of the headlamps as a function of thebrightness of light sources within the images; and a user inputmechanism coupled to the control circuit for allowing a user to adjust asensitivity at which the control circuit will control the headlamps inresponse to light sources within the images.

According to yet another aspect of the invention, a headlamp controlsystem is provided for controlling the headlamps of a controlled vehiclethat comprises an imaging system configured to image the scene forwardof the controlled vehicle and to detect an ambient light level outsidethe vehicle, and a control circuit coupled to the imaging system fordetermining an ambient light level outside the vehicle, for identifyingand determining the brightness of light sources in images obtained fromthe imaging system, and for controlling the headlamps to vary a beampattern of the headlamps as a function of the brightness of lightsources within the images when the ambient light level is above athreshold level.

According to another aspect of the present invention, a control systemis provided to control exterior lights of a vehicle. The control systemcomprises an image array sensor including a plurality of pixels, anoptical system configured to image the scene forward of the controlledvehicle onto the image array sensor, the optical system including aforwardmost surface, and a control circuit for processing the image ofthe scene obtained from the image array sensor and for controlling theexterior lights in response to objects detected in the processed scene,wherein the optical system includes a hydrophilic coating on theforwardmost surface.

According to yet another aspect of the present invention, a vehiclecontrol system is provided to control the brightness of continuouslyvariable headlamps that have a brightness that varies continuouslybetween a high beam state and a low beam state. The control systemcomprises an imaging system configured to image the scene forward of thecontrolled vehicle, a control circuit for identifying and determiningthe brightness of light sources in images obtained from the imagingsystem and for controlling the brightness of the headlamps as a functionof the brightness of light sources within the images, and an indicatorcoupled to the control circuit and positioned inside the vehicle forindicating to the driver the relative brightness of the headlamps.

According to another aspect of the invention, an imaging system for avehicle is provided that comprises an image sensor having an array ofpixels and at least one other component, and an optical baffle disposedbetween the images sensor and a scene to be imaged for preventing lightfrom the scene from reaching the at least one other component.

According to a further aspect of the invention, a headlamp controlsystem for a vehicle is provided that comprises an imaging systemconfigured to image the scene forward of the controlled vehicle, aswitching mechanism for manual input of a driver's selection of afeature affecting the control of the vehicle headlamps, and a controlcircuit coupled to the switching mechanism and the imaging system foridentifying and determining the brightness of light sources in imagesobtained from the imaging system and for controlling the brightness ofthe headlamps as a function of the brightness of light sources withinthe images and as a function of the status of the switching mechanism.

Another aspect of the present invention is to provide a headlamp controlsystem for a vehicle that comprises a control circuit coupled to thevehicle headlamps for fading the headlamps of the vehicle to an offstate in response to the turning off of the vehicle ignition or exitingthe vehicle.

According to another aspect of the invention, a control system isprovided to control exterior lights of a vehicle. The control systemcomprises an image array sensor including a plurality of pixels, anoptical system configured to image the scene forward of the controlledvehicle onto the image array sensor, the optical system including aforwardmost surface, and a control circuit for processing the image ofthe scene obtained from the image array sensor and for controlling theexterior lights in response to objects detected in the processed scene,the optical system includes a photocatalytic coating on the forwardmostsurface.

Another aspect of the present invention is to provide a control systemto control the headlamps of a vehicle. The control system comprises amanually actuated switch mechanism for receiving input from a driver totemporarily increase the brightness of the vehicle headlamps in aflash-to-pass state, an ambient light sensor for sensing the ambientlight outside the vehicle, and a control circuit coupled to the ambientlight sensor and the manually actuated switch mechanism for varying thebeam pattern of the headlamps during the flash-to-pass state in responseto the ambient light level sensed by the ambient light sensor.

According to yet another aspect of the present invention, a controlsystem is provided to control the headlamps of a vehicle where thevehicle has a microwave receiver for receiving signals from satellites.The control system comprises a control circuit for receiving signalsfrom the microwave receiver indicative of the location of the vehicle,the control circuit controls the headlamps to limit the perceivedbrightness of the headlamps from exceeding a predetermined level lessthan their capacity when the vehicle is travelling on a residentialstreet.

These and other features, advantages, and objects of the presentinvention will be further understood and appreciated by those skilled inthe art by reference to the following specification, claims, andappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter that is regarded as the invention is particularlypointed out and distinctly claimed in the claim portion that concludesthe specification. The invention, together with further objects andadvantages thereof, may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, wherelike numerals represent like components, and in which:

FIG. 1 illustrates vehicles traveling on a common road;

FIGS. 2 a and 2 b illustrate an optical sensor system, FIG. 2 b showinga perspective view and FIG. 2 a showing a cross section of the opticalsensor system taken along plane 2 a—2 a in FIG. 2 b;

FIG. 3 is a plan view illustrating an image sensor used in the opticalsensor system according to FIGS. 2 a and 2 b;

FIG. 4 is a top plan view illustrating a lens structure used in theoptical sensor system according to FIGS. 2 a and 2 b;

FIG. 5 is a side elevation view illustrating the lens structureaccording to FIG. 4;

FIG. 6 is a graph illustrating wave transmissivity as a function oflight wavelength for the lens;

FIG. 7 shows a light sensitive surface of the image sensor andillustrates the regions of the image array which are impacted by thelight from each of the lenses;

FIG. 8 is a cross section illustrating another image sensor assemblytaken along the same plane as the assembly in FIG. 2 a;

FIG. 9 is a cross section illustrating yet another light sensor assemblytaken along the same plane as the assembly in FIG. 2 a;

FIG. 10 is a partial cross section of a rearview mirror assemblyillustrating an optical sensor system;

FIG. 11 is a circuit schematic illustrating a circuit for an opticalsensor system and an electrochromic mirror;

FIG. 12 is a circuit schematic illustrating a headlamp drive for thecircuit according to FIG. 11;

FIG. 13 is a circuit schematic illustrating a microcontroller circuitfor the circuit according to FIG. 11;

FIG. 14 is a flow chart illustrating operation of an electrochromicmirror and headlamp control;

FIG. 15 is a flow chart illustrating operations to acquire and analyzean image;

FIG. 16 is a flow chart illustrating operations to analyze an image andfind a light source;

FIG. 17 a is a flow chart illustrating a seed fill algorithm;

FIG. 17 b illustrates a pixel array impacted by a light source;

FIG. 18 is a flow chart illustrating operation to determine if lightsources are oncoming or preceding vehicles;

FIG. 19 is a state diagram illustrating the duty cycle associated withstates for a variable high beam lamp;

FIG. 20 illustrates operation rules for changes of state in FIG. 19;

FIG. 21 is a flow chart illustrating operation to provide speed varyingthresholds;

FIG. 22 is a chart illustrating the different regions of the imagearray;

FIG. 23 is a flow chart illustrating operation of the microcontroller toshift the regions in FIG. 22;

FIG. 24 is a front perspective view illustrating an image sensorassembly including an electronically alterable filter;

FIG. 25 is a side elevation view of the liquid crystal filter in theimage sensor assembly according to FIG. 24;

FIG. 26 a is an exploded perspective view illustrating an LED headlamp;

FIG. 26 b is a fragmentary cross section taken along plane 26 b—26 b inFIG. 26 a;

FIG. 26 c is a front plan view illustrating an alternate embodiment ofan LED lamp;

FIG. 26 d is a fragmentary cross section taken along plane 26 d—26 d inFIG. 26 c;

FIG. 27 is a top, front perspective view of an LED headlamp forprojecting light in more than one horizontal direction;

FIG. 28 is a top, front perspective view of an LED headlamp forprojecting light in more than one vertical direction;

FIGS. 29 a—29 d illustrate a method of manufacturing surface mountedfilters for an image sensor;

FIG. 30 is a chart illustrating the wavelengths passed by a red filtersurface mounted to an image sensor;

FIG. 31 is a chart illustrating the wavelengths passed by a cyan filtersurface mounted to an image sensor;

FIG. 32 illustrates another image sensor assembly;

FIG. 33 illustrates an electrical system including a wave sensitiveheadlamp control;

FIG. 34 is a circuit schematic illustrating an alternative circuit foran optical sensor system and an electrochromic mirror;

FIG. 35 is a state diagram illustrating a first control scheme formanually or automatically controlling the vehicle headlamps in responseto activation of various manual switches;

FIG. 36 is a state diagram illustrating a second control scheme formanually or automatically controlling the vehicle headlamps in responseto activation of various manual switches;

FIG. 37 is a state diagram illustrating a third control scheme formanually or automatically controlling the vehicle headlamps in responseto activation of various manual switches;

FIG. 38 illustrates an exemplary indicator for use with the headlampcontrol system of the present invention;

FIG. 39 is a representative pictorial view of an imaged scene taken inseveral superimposed frames;

FIG. 40 is a functional block diagram of one embodiment of the presentinvention;

FIG. 41 is front elevational view of a mirror mount accessory housingaccording to another embodiment of the present invention;

FIG. 42 is top plan view of the mirror mount accessory housing shown inFIG. 41;

FIG. 43 is a cross-sectional view of the mirror mount accessory housingshown in FIGS. 41 and 42 taken along line 43-43′ in FIG. 42;

FIG. 44 is an exploded perspective view of the mirror mount accessoryhousing;

FIG. 45 is rear elevational view of the mirror mount accessory housing;

FIG. 46 is a side elevational view of the mirror mount accessory housingwith the housing cover removed;

FIG. 47 is a top plan view of the mirror mount accessory housing withthe housing cover removed;

FIG. 48 is a front elevational view of the mirror mount accessoryhousing with the housing cover removed;

FIG. 49 is a rear elevational view of the mirror mount accessory housingwith the housing cover removed; and

FIGS. 50A-50C are pictorial representations of various illuminationpatterns produced by exterior lights of a vehicle.

DETAILED DESCRIPTION OF THE INVENTION

The present invention generally pertains to a control system forcontrolling the exterior lights of a vehicle. As noted above, suchexterior lights may include headlamps, tail lights, foul weather lightssuch as fog lights, brake lights, center-mounted stop lights (CHMSLs),turn signals, back-up lights, cargo lights, puddle lights, license plateilluminators, etc. The headlamps may be operated in several differentmodes including conventional low-beam and high-beam states. They mayalso be operated as daytime running lights, and additionally assuper-bright high beams in those countries where they are permitted. Theheadlamp brightness may also be continuously varied between the low,high, and super-high states. Separate lights may be provided forobtaining each of these headlamp states or the actual brightness of theheadlamps may be varied to provide these different headlamp states. Ineither case, the “perceived brightness” of the headlamps is varied. Asused herein, the term “perceived brightness” means the brightness of theheadlamps as perceived by an observer outside the vehicle. Mosttypically, such observers will be drivers or passengers in a precedingvehicle or in a vehicle traveling along the same street in the oppositedirection. Ideally, the exterior lights are controlled such that if anobserver is located in a vehicle within a “glare area” relative to thevehicle (i.e., the area in which the observer would perceive thebrightness of the exterior lights as causing excessive glare), the beamillumination pattern is varied such that the observer is no longer inthe glare area. The perceived brightness and/or glare area of theheadlamps (and/or other exterior lights) may be varied by changing theillumination output of one or more lights forming the headlamps, bysteering one or more lights to change the aim of one or more of thelights forming the headlamps, activating or deactivating some or all ofthe lights, altering the illumination pattern forward of the vehicle, ora combination of the above. FIG. 50A shows a typical low beam pattern aswould be used when other vehicles are nearby and forward of thecontrolled vehicle 5000. FIG. 50B shows an examplary composite beampattern including both high and low beam patterns and side bending lightpatterns, which may be individually activated as the vehicle 5000approaches a turn. FIG. 50C illustrates another composite beam patternincluding a low beam pattern and an intermediate, side-aimed pattern,which may be produced by changing the focus or aim of the high beams aswell as the brightness of the high beams. The composite beam patternshown in FIG. 50C is useful when another vehicle is approaching in anoncoming and adjacent lane. As will be apparent to those skilled in theart, a large number of other beam patterns can be achieved using knownheadlamp mechanisms. Other mechanisms for adjusting the perceivedbrightness and glare area of the headlamps will also be apparent tothose skilled in the art.

Although the present invention primarily addresses the control of thevehicle headlamps, embodiments are described below for controlling thetail lights and foul weather lights. In some embodiments, the presentinvention is generally described as controlling the “exterior lights,”which broadly includes any exterior lighting on the vehicle. Forexample, the present invention may be used in some circumstances tocontrol the perceived brightness of a turn signal mounted in an outsiderearview mirror assembly so as to provide sufficient light output forsignaling a driver in another vehicle without causing excessive glare inthe eyes of the driver of the vehicle having the signal mirrors. Also,the present invention may be employed to control the instrument panellights as well as other interior display lights based upon the sensedambient light. Other examples will be apparent to those skilled in theart.

A controlled vehicle 100 (FIG. 1) having an automatic headlamp dimmerincludes an optical sensor system 102 for detecting the headlamps 104 ofan oncoming vehicle 105 and the tail lights 108 of a preceding vehicle110. The headlamps 111 of the controlled vehicle 100 are controlledautomatically to avoid shining the high beams, or bright lights,directly into the eyes of a driver of oncoming vehicle 105 or byreflection into the eyes of the driver of the preceding vehicle 110. Theoptical sensor assembly 102 is illustrated mounted in the windshieldarea of the vehicle, but those skilled in the art will recognize thatthe sensor could be mounted at other locations that provide the sensorwith a view of the scene in front of the vehicle. One particularlyadvantageous mounting location is high on the vehicle windshield toprovide a clear view, which view can be achieved by mounting the opticalsensor assembly 102 in a rearview mirror mount, a vehicle headliner, avisor, or in an overhead console. Other views that may be advantageouslyemployed include mounting the optical sensor assembly 102 on theA-pilar, the dashboard, or at any other location providing a forwardviewing area. However, the most advantageous mounting locations arethose that position the image sensor to view a forward scene through anarea kept clean by the vehicle's windshield wipers.

With reference to FIGS. 2 a and 2 b, the optical sensor assembly 102includes an electronic image sensor 201 and an optical system to directlight onto the image sensor 201. The image sensor 201 generallycomprises an array of light sensitive components and associatedcircuitry to output electronic pixel light level signals responsive tolight impacting on the surface of the image sensor 201. The opticalsystem generally contains four components: lens structure 202; aperturestop member 203; far field baffle 204; and optional infrared filter 206.The optical system controls the scene viewed by the image sensor 201. Inparticular, the optical system focuses light rays 205 passing throughopening 207 of the far field baffle onto the array 201 contained withinthe image sensor assembly 201.

The Image Sensor

The configuration of the image sensor 201 is illustrated in FIG. 3. Theimage sensor includes an image array 301 (FIG. 3) that can be made fromany one of a variety of sensors, such as CMOS image sensors, chargecoupled device (CCD) image sensors, or any other suitable image sensor.In one embodiment, the image sensor is a CMOS photogate active pixelimage sensor. A CMOS photogate active pixel image sensor is described inU.S. Pat. No. 5,471,515, entitled ACTIVE PIXEL SENSOR WITH INTER-PIXELCHARGE TRANSFER, issued to Eric R. Fossum et al., on Nov. 28, 1995, thedisclosure of which is incorporated herein by reference thereto. Sensorsystems including arrays are disclosed in U.S. patent application Ser.No. 09/448,364, entitled CONTROL CIRCUIT FOR IMAGE SENSORS, filed Nov.23, 1999, by Jon Bechtel et al., now U.S. Pat. No. 6,469,739; U.S.patent application Ser. No. 08/933,210, entitled CONTROL CIRCUIT FORIMAGE SENSORS, filed on Sep. 16, 1997, by Jon Bechtel et al., now U.S.Pat. No. 5,990,469; and U.S. patent application Ser. No. 08/831,232,filed Apr. 2, 1997, entitled CONTROL SYSTEM TO AUTOMATICALLY DIM VEHICLEHEADLAMPS, by Joseph Stam et al., now U.S. Pat. No. 5,837,994, thedisclosures of this application and patents are incorporated herein byreference thereto.

The array 301 may for example comprise photogate active pixels, such as10 to 50 μm pixels. It is advantageous for the array to be a lowresolution array, which is an array that has a resolution of less than7000 pixels per square millimeter and more preferably less than 2500pixels per square millimeter. The array may have 25 μm or largerphotogate active pixels. In particular, the array may include 30 μm orlarger pixels arranged in a grid smaller than 200 rows by 200 columns,and may advantageously comprise a rectangular array having 64 columnsand 80 rows of pixels. Such an image sensor is described in detail inU.S. Pat. No. 5,471,515 incorporated herein above by reference thereto.The optically active region of array 301 is approximately 1.9 mm in theX direction by 2.4 mm in the Y direction. Using such a low resolutionimage sensor array to monitor the forward field of the controlledvehicle 100 results in a relatively low resolution sensor system thatcan be supported by high speed processing in a cost effective mannerwhile enabling a vehicle headlamp control to be highly reliable andaccurate. The low resolution array reduces the memory and processorrequirements of associated circuitry. The use of such larger pixelsincreases sensitivity and thus allows the use of slower, and thus lowercost, optics. However, one skilled in the art will recognize that theuse of a higher resolution array with smaller pixels may be advantageousto reduce the area of the sensor array and thus potentially reduce thecost at the array itself. In the case where a high resolution imagesensor is employed, faster components and higher quality optics may berequired to accommodate the high resolution image sensor. With advancesin optical manufacturing, such optics may become cost effective suchthat use of a higher resolution array becomes economically practical.Additionally, it is expected that in future years the cost of aprocessor and memory required to process an image containing more pixelswill be reduced making a higher resolution system feasible. A higherresolution array may improve the ability to detect distant tail lamps.However, at this time it is preferred to use a low resolution array withrelatively few pixels to maintain the economy of the invention and thusenable widespread acceptance in the market place.

An image sensor and control circuit therefore will be described ingreater detail herein below, and such a system is disclosed in U.S. Pat.No. 5,990,469, the disclosure of which is incorporated herein above byreference.

In addition to the array 301, the image sensor 201 includes: serialtiming and control circuit 309; column output circuit 302; biasgenerating digital-to-analog converters (DACs) 305; flashanalog-to-digital converters (ADCs) 304; and analog amplifier 303.Serial timing and control circuitry 309 provides a high-speedsynchronous bi-directional interface between a microcontroller 1105(FIG. 11) and the image sensor 201. As described in U.S. Pat. No.5,990,469, the control circuit 309 allows the microcontroller 1105 tooutput parameters that control the selection of pixels exposed formeasurement (i.e., selects the area of array 301 exposed; which area isreferred to herein as the “window”); exposure time which affectssensitivity; bias voltages generated by the bias voltage generation DACs305; and the analog gain of amplifier 303. Additional features includethe ability to expose two windows simultaneously, using the same ordifferent gain settings for the amplifier 303 for pixels of therespective windows, and the ability to acquire a sequence of multipleframes. The control circuit 309 also enables a sleep feature thatdisables the analog components of the image sensor assembly 201 toreduce power consumption when the image sensor is not in use. The imagesensor also includes: a power supply input Vdd; a ground input; serialdata bus input/output (I/O) 308; serial data clock I/O 311; slave selectinput 307; and clock input 306.

The Lens Structure

Lens structure 202 (FIG. 2 a) includes lenses 208 and 209. Although twolenses are disclosed, the image sensor 201 could use a single lens ormore than two lenses. The two lenses 208, 209 are used to produce twodifferent images of the same scene through different color filters toassist in properly discriminating headlamps from tail lamps using theimage sensor 201 as described below and in U.S. Pat. Nos. 5,837,994 and5,990,469, the disclosures of which are incorporated herein above byreference. The image system allows the acquisition of an image of ascene through at least one color filter 208, 209. In one embodiment, thelens structure is constructed to image the forward scene onto one regionof the image array 301 through a first color filter and to image theforward scene onto another region of the image array through a secondfilter. For example, filter 209 (FIGS. 2 a and 2 b) may be a red filterand filter 208 may be either a blue filter, a green filter, a cyanfilter, a clear filter (which is for example the absence of a colorfilter), or any other suitable filter. There are various places withinthe optical system that the filters could be incorporated other than thelens 208, 209, such as on the image sensor surface. However,incorporating the filters into the lens structure has the advantage thatthe light is not focused at the point of the filter. Locating the filterin the image plane, i.e., on the sensor, would leave an organic filtersusceptible to thermal damage should the sun fall within the sensor'sfield of view such that the sun's rays are focused on the filters.Typically, filter materials are much more vulnerable to thermal damagethan the image sensor itself. A possible exception would be dichroicinterference filters, which are highly resistant to thermal damage. Amethod by which such thermal resistant filters can be deposited onto asemiconductor image sensor surface is described in greater detail hereinbelow with respect to an alternate embodiment of the present invention.

An example of a filter that could be incorporated on the image sensorsurface is a dichroic filter array of the type disclosed in U.S. Pat.No. 5,711,889 to Philip E. Buchsbaum, the entire disclosure of which isincorporated herein by reference. The dichroic filter array disclosed inthis U.S. patent is resistant to thermal damage and therefore would besuitable for use in an image sensor used for detecting light sources inthe control of a vehicle's headlamps. Such a dichroic filter array mayinclude a checkerboard or mosaic pattern may be deposited on to thearray such that neighboring pixels are exposed to separate bands oflight. A technique for depositing interference filters of differentcolors onto neighboring pixels is disclosed in the above-referenced U.S.Pat. No. 5,711,889. In one embodiment, neighboring pixels arealternatively coated with a red filter (R) and no filter (clear (C)) asillustrated in the table below.

R C R C C R C R R C R C C R C R

In this embodiment, the optics do not include the lens structure andcolor filters discussed above, since the color filtering function isperformed by the filter pattern. Likewise, the optics do not need toseparately image the forward scene onto two portions of the imagesensor. Thus, the twice as much of the image sensor array may be used toimage a single image of the forward scene. It should be noted however,that in accordance with yet another embodiment of the present invention,the optics may still image the forward scene onto two separate portionsof the image sensor array as discussed above, but instead ofincorporating the color filter into the lens, the color filter may beprovided as a patterned or non-patterned multi-layer interference filteron the sensor.

The optics in this embodiment are slightly defocused such that the spotsize from a distant point light source covers at least two pixels. Inthis way, an accurate reading of the red component of the object can bedetermined. The inventors have discovered that common color filter arraytechnologies, typically employing polymer filters, will not withstanddirect focused sunlight. In many automotive applications, the sun may befocused onto the array if a vehicle is traveling or parked such that thesun is within the field of view of the camera. Interference filters arefar more robust and reflect the unwanted spectral bands of light ratherthan absorb them. As a result, their use overcomes the limitations ofthe prior filtering technologies and allows the construction of anautomotive camera. These filters can be used not only with cameras whichare used in applications which control vehicle equipment, but also inapplications where images are acquired and displayed to the driver forvisual assistance.

In another embodiment, three-color interference filters can be used toconstruct a red, green, and blue (RGB) pixel array (or theircomplements) as illustrated in the table below.

G R G R B G B G G R G R B G B G

A full color value for each pixel is determined by using the color ofthe current pixel and interpolating the other two colors fromneighboring pixels with different filter colors. Techniques forperforming this interpolation are well known in the art. In a simplerscheme, groups of four pixels are treated as one “super pixel.” The lensis defocused enough such that the image of a point light source isblurred over a 2×2 block of pixels. For each block of 2×2 pixels, thered, green, and blue color components are determined from the individualpixels. This data can be represented either as three separate values oras an intensity and color value.

The use of a 2×2 super pixel simplifies processing and reduces the totalnumber of values stored. This technique can be combined with any of theother techniques in an application requiring color imaging. For anapplication such as a high beam headlamp control system, traditionalcolor interpolation can be used near the center of the image forincreased resolution and the technique of using super pixels can be usedaway from center. Super pixels larger than 2×2 blocks can be used wheresubstantially decreased resolution is acceptable.

The lens structure 202 will now be described in greater detail withreference to FIGS. 2 a, 4, 5, and 7. The lens structure 202 includes afirst lens 208 and a second lens 209 that focus light from othervehicles onto the image array 301 (FIG. 7). The two lens elements 208,209 image the forward scene onto different respective regions 702, 703of the image sensor image array 301. Each lens element 208, 209 containsa spectral band pass filter, such that the forward image scene projectedonto the respective regions of the image array 301 each represents adifferent color component of the image, where it is advantageous todetermine the relative color of objects in the field of view. It isparticularly advantageous for the lens elements 208 (FIG. 2 a) and 209to comprise cyan and red filters, respectively, as mentioned above andshown in FIGS. 4 and 5. Alternatively, it may be advantageous for lens209 to contain a red spectral filter and for lens 208 to be clear.

The sensor system may for example employ lens elements 208 and 209 thatare 0.5 mm to 2.5 mm in diameter, and may advantageously comprise lensesthat are 1.0 to 2.5 mm in diameter, such as being 2.2 mm in diameter. Inthe Y direction, the lens center axes C₁ and C₂ may be spaced by 0.6 to1.6 mm, and may for example be spaced by 1.1 to 1.4 mm, and mayadvantageously be spaced 1.3 mm in the Y direction (as indicated in FIG.5). A portion of the lens may be truncated on one side to achieve thisspacing. The lens center C₁, C₂ may be aligned in the X direction asshown in FIG. 4, or be offset. Lens element 208 may for example includea cyan filter with an aspheric lens having a curvature of 0.446 mm⁻¹ anda conic constant of −0.5 to achieve the desired focal length. Lenselement 209 may in contrast, be a red filter, aspheric lens with acurvature of 0.450 mm⁻¹ and a conic constant of −0.5 to achieve the samedesired focal length. At the center, each lens is 0.5 to 1.5 mm thick,and may advantageously be 1.0 mm thick. The difference in curvature ofthe two lenses compensates for the dispersion in the lens material andoptimizes each lens for the spectral band passed by the filter. Theseparameters result in a lens with an effective focal length of 4.5 mm andthus have an F# of 2. It will be recognized that these optics areexemplary, and that other optics could be provided, such that the focallength and F# could be different.

The lens structure 202 may be molded out of a light-transmissive plasticsuch as acrylic, manufactured from glass, or may be produced by anyother suitable construction. Where the lenses 208, 209 are molded fromplastic, the filters may be formed integrally with the plastic by theinclusion of dyes within the material or they may be molded of a cleartransparent material, particularly where the image sensor has a surfacemounted filter as described herein below. An example of an acrylicmaterial, which includes a red filter dye, is part number RD-130available form OptiColor, Inc. of Huntington Beach, Calif., USA. Anacrylic material incorporating a cyan filter is OptiColor part numberBL-152. The spectral transmission of these two materials is shown inFIG. 6. Using the optional infrared filter 206 will remove light withwavelengths greater than approximately 700 nm.

The lens structure 202 including integral filters may be manufacturedusing a bi-color injection molding process. First one-half of the lens,for example the red half including lens 209, is molded in a toolcontaining features to form the red half of the lens. Next, the moldedred half of the lens is inserted into a tool containing features for thecyan half of the lens structure 202 in addition to features to hold thered lens 209. The cyan lens 208 half of the lens structure 202 is theninjection molded against the red lens 209 half forming one bi-colorlens. Alternatively, each of the lenses 208 and 209 can be provided bylens elements such as disclosed in copending U.S. Pat. No. 6,130,421,entitled IMAGING SYSTEM FOR VEHICLE HEADLAMP CONTROL, filed Jun. 9,1998, by Jon H. Bechtel et al., the disclosure of which is incorporatedherein by reference thereto.

While red and cyan filtered lens elements are used in the illustratedembodiment, other combinations of lenses may also be suitable for thisapplication. For example, it is possible to replace cyan lens element,208 with a clear lens. Also, it is possible to use three lenses withrespective color filters, and in particular red, green, and bluefilters, to obtain a full color image. Such an arrangement could use asequence of three lenses aligned along the Y axis of FIG. 4, with onelens positioned on the center axis and the other two lenses positionedadjacent this center lens. The spacing of the lenses mightadvantageously be uniform to provide uniformly spaced regions on thelight sensitive surface of the image array 301. The red and cyan filtercolors described above are thus only presented herein as an example, andany combination of filters which pass at least two isolated oroverlapping spectral bands of light and allow for the distinction oftail lamps from headlamps may be used. Those skilled in the art willrecognize that other methods can be used to incorporate the filters,such as screen printing dyes applied to the flat back surface of thelens structure 202, or application of a filter material to the surfaceof a clear lens structure. Additionally, an advantageous system using asingle lens is described herein below with reference to FIGS. 24 and 25.

The Aperture Stop

Aperture stop 203 comprises an opaque member, including apertures 240(FIG. 2 a) and 242, positioned over lenses 208, 209. The aperture stop203 can be manufactured of any suitable material, such as moldedplastic, and it can be painted or otherwise treated so as to block thepassage of light if the material of which the plastic is manufactured isnot opaque. Aperture stop 203 defines the apertures 240, 242 for lenselements 208 and 209. Aperture stop 203 also prevents passage of straylight through regions of lens structure 202 other than the lens elements208 and 209. It will be recognized that the aperture stop 203 can bepaint applied directly to the surface of lens structure 202, andoptionally to the sidewalls of light sensor assembly 250, such that thepaint blocks passage of stray light through regions of lens 202 otherthan the lens elements 208 and 209. The aperture stop may also bestamped from a rigid material such as Mylar and placed over the lensstructure. Such an aperture stop may include a pair of registrationholes for engaging posts extending from the lens structure such that theaperture stop may be properly positioned relative to the lens structurewith the apertures 240, 242 aligned with the corresponding lens elements208, 209 of lens structure 202.

The aperture stop and/or the window may define a transparent window inan otherwise opaque mask in which the transition from the opaque regionto the transparent region may be graded. By providing such a gradient,spatial thresholding of the received and processed image may be readilyaccomplished. The purpose for such spatial thresholding is discussed inmore detail below.

The Far Field Baffle

The far field baffle 204 (FIGS. 2 a and 2 b) is an opaque enclosure tobe positioned over the image sensor 201. The baffle includes an opening207, which is the sole light passage into the image sensor. Theillustrated far field baffle 204 is a generally rectangular boxincluding four sidewalls 215 (only two of the four being visible in FIG.2 b), an end wall 217 including opening 207, and an open end 219. Theopen end is secured to the support 220 on which image sensor 201 iscarried. The support 220 may be, for example, a circuit board orhousing, and is preferably opaque to block the passage of light into thechamber defined by the far field baffle. The walls 215, 217 of the farfield baffle 204 are opaque, and may be of any suitable constructionsuch as stamped from metal, molded from plastic, or the like. If thematerial from which the walls are made is not opaque, it may be paintedor otherwise treated to block the admission of light. The far fieldbaffle defines the forward scene viewed by image sensor array 208. Theside walls 215 and end wall 217 prevent light at angles outside of thedesired field of view from entering and are also used to keep lightinput through one lens from crossing over to the region of the arrayreserved for the other lens. The far field baffle aperture 207 isideally about 4-6 focal lengths, or approximately 18 mm in theillustrated embodiment, from the front of the lens (for the sake ofclarity, the figures of the application are not to scale). The field ofview through aperture 207, aperture stop 203, and lenses 208 and 209, inthe illustrated embodiment, is about 10° in the vertical direction and25° in the horizontal direction in front of the vehicle. This field ofview can be achieved with a rectangular or elliptical far field baffleopening 207 that is 6 to 7 mm in the Y direction and 9 to 10 mm in the Xdirection, in the above described embodiment.

In particular the far field baffle 204 has an opening 207 in an end wall217. The sidewalls 215 of the image array sensor extend orthogonallyfrom the end wall 217. The walls 215, 217 may be formed integrally in amolding or stamping process or they may be joined after constructionusing an adhesive, fasteners or the like. The far field baffle ispreferably a black plastic molded member, although it may be providedusing any material that will absorb most or all of the light strikingthe sidewalls. By providing wall surfaces on the inside of the far fieldbaffle that absorb light, the walls will not reflect light that entersthough opening 207 onto the image array sensor 201. In the illustratedembodiment, the baffle is rectangular, but those skilled in the art willrecognize that the baffle could be square, cylindrical, or any othersuitable shape. An imaging system including a far field baffle isdescribed in co-pending U.S. Pat. No. 6,130,421, entitled IMAGING SYSTEMFOR VEHICLE HEADLAMP CONTROL, filed on Jun. 9, 1998, by Jon H. Bechtelet al, the disclosure of which is incorporated herein by referencethereto.

Far field baffle 204 and aperture stop 203 preferably configured toprevent light from reaching components other than image sensor array 201that may be mounted on circuit board 221. Certain sensors, such as CMOSsensors, often include other components besides the image sensor arrayon the printed circuit board that may be damaged from exposure to light.Additional baffle structures may be incorporated for this purpose.

Infrared Filter

The far field baffle holds an optional infrared filter 206 (FIG. 2 a).Infrared filter 206 prevents light of wavelengths longer than about 700nm from being imaged by the optical system. This is advantageous aslight above 700 nm (FIG. 6) will pass through the red and cyan filters.By removing this light, the only light that will be considered isvisible light in the pass band of the red and blue filters. The infraredfilter has become more important due to the recent commercialization ofLED tail lamps. Because incandescent light sources emit infrared lightwhile LED light sources do not, the infrared filter is desirable tobalance out the detected brightness of these two types of light sources.

Infrared filters are available from Optical Coating Laboratories ofSanta Rosa, Calif., and are called Wide Band Hot Mirrors. The infraredfilter 206 may be mounted to the end wall 217 using an adhesive,mechanical fasteners such as a snap connector, or the like, and may sealoff the chamber within the far field baffle to prevent dust and moisturefrom entering the system and degrading the performance of the system.

Alternatively infrared filter 206 may be incorporated as a dye withinthe lens, a coating on the lens, a coating on the image sensor surface,a lid on an image sensor package, or elsewhere in the image sensorassembly. If the IR filter is not such that it can be used to close theopening 217 of far field baffle 204, it may be desirable to place aclear window, such as glass, plastic, or the like in the opening 217 toprevent dust from entering into the interior of the far field baffle andinterfering with the performance of the sensor system 102.

Hydrophilic/Photocatalytic Coatings

In addition to functioning as an infrared filter, filter 206 serves toprevent debris and liquid from reaching the image sensor assemblythrough opening 207. In the event an infrared filter is not utilized, atransparent window may be used in its place for this purpose.

Whether an infrared filter 206 or window is utilized, it is desirable tokeep liquid drops from attaching to the outer surface of filter/window206 within opening 207 since such liquid drops distort the image that isreceived and processed by the image sensor and because such liquid dropstend to dry and leave spots on the outer surface of filter/window 206.Such liquid drops may form on filter/window 206 when, for example, anindividual sprays a cleaning fluid on the inside of the windshield,which is in close proximity to the outer surface of filter/window 206.It is very possible that the individual cleaning the windshield wouldforget to wipe the cleaning fluid from the filter/window of the imagesensor, thus leaving a fine mist of water droplets over the surface ofthe filter/window, which would blur the images obtained by the imagesensor.

To overcome this problem, the present invention may employ a hydrophiliccoating on the outer surface of filter/window 206. Hydrophilic coatingshave a porous outer layer(s) that absorb the water or other liquiduniformly across its surface such that water droplets/spots do not formon its surface. One problem many such hydrophilic coatings experience isthat the pores in the outer layer(s) may become clogged by oil, grease,or other contaminants thereby eliminating the effectiveness of thehydrophilic coating. To overcome that problem, a photocatalytic layermay be used in conjunction with the hydrophilic coating. Suchphotocatalytic layers break down the oil, grease, or other contaminantswithin the hydrophilic layer when exposed to ultraviolet light. Thistends to clear the pores in the hydrophilic layer of the contaminant andallow it to operate effectively as a hydrophilic layer. Examples ofhydrophilic/photocatalytic coatings that may be employed for thispurpose are disclosed in U.S. patent application Ser. No. 09/602,919entitled ELECTRO-OPTIC DEVICE HAVING A SELF-CLEANING HYDROPHILIC COATINGfiled on Jun. 23, 2000, by William L. Tonar et al. The entire disclosureof this application is incorporated herein by reference.

Assembly of the Image Sensor Assembly

Assembly of the image sensor will now be described with reference toimage sensor assembly 801 of FIG. 8, which is identical to the imagesensor assembly 250 except for the gel 805 in image sensor assembly 801.The image sensor 201, lens structure 202, and aperture stop 203 arecombined to form an integral image sensor assembly 250 (FIG. 2) or 801(FIG. 8). The image sensor 201, which is advantageously a singleintegrated circuit (IC), is attached to printed circuit board 220 by anysuitable conventional means such as using chip-on-board technology.Connections to the image sensor chip are made by any suitable means,such as wire bonds 804. The bonded IC is then optionally covered with anoptically clear stress relieving gel 805. Examples of materials that canbe used for this coating are Silicon Semi-Gel type C from Transene Co.of Danvers, Mass., or Dielectric Gel 3-6211 from Dow Coming Corp. ofMidland, Mich. The coated IC is then encapsulated in a hard opticallyclear enclosure 802, which may for example comprise epoxy. The epoxy isformed into a desired shape and may form, for example, a cube. The cubecan be dimensioned to occupy a very small volume, and may for examplehave length and width dimensions of about 1 cm on a side, and athickness of about 5 mm. The enclosure 802 (FIG. 8) may be selected tohave approximately the same index of refraction as the stress relievinggel 805 to prevent any refraction at the interface between these twomaterials. Examples of suitable epoxies are: Epo-Tek 301-2FL from EpoxyTechnology, Inc. of Billerica, Mass., Epoxy 50 from Transene Co, orDexter-Hysol OS 1900, or 300H from Nitto Denko Corporation. If thecoefficient of thermal expansion of the enclosure 802 is sufficientlylow that its expansion and contraction will not break wire bonds 804 atthe expected operating temperature range for the image array sensor 201,stress-relieving gel 805 can be omitted, as is shown by enclosure 230over wire bonds 234 in image sensor assembly 250 in FIG. 2 a.

Lens structure 202 is attached to the enclosure 802 (FIG. 8) orenclosure 230 (FIG. 2) using a UV curable optically clear adhesive 232.UV curable adhesive 232 is dispensed onto the epoxy cube 802 and lens202 is juxtaposed with UV curable adhesive 232. Lens structure 202 isspaced from the image sensor 201 by a distance such that images at“infinity” are focused on the desired image regions 702 and 703. The UVcurable adhesive 232 is exposed to UV light and cured, locking lensstructure 202 into position and permanently attaching lens structure 202to enclosure 802. The total distance between the back surface of thelens structure 202 and the top of the image sensor 201 die is 6.7 mm inthe illustrated example. This distance is significantly longer than theeffective focal length of 4.4 mm because the entire optical path betweenthe back of the lens 202 and the front of the image array 201 is througha material with a higher index of refraction than air. Ideally theprocess of aligning the lens to the image sensor and curing the UVadhesive to hold it in place is accomplished while actively focusing thelens to accommodate variations in the manufacture of the lens and otherimage sensor assembly components. This process is accomplished bypowering the image sensor during assembly and acquiring images of a farfield scene from the image sensor into a host computer. The UV curableadhesive is dispensed onto the surface of the sensor and the lens ispositioned on the UV curable adhesive using a multi-axis robot orpositioner. The position of the lens is adjusted by the robot until theimages acquired by the sensor appear in focus. At this point, the UVcurable adhesive is exposed to UV light, cementing the lens into place.Micropositioning equipment suitable for this purpose is available fromPhysik Instremente GmbH and Company of Germany.

UV curable adhesive 232 serves to fill the space between the lens 202and enclosure 802, and thus fills in any ripples or other non-planarsurfaces of enclosure 802 thereby precluding the creation of air gapsbetween the lens 202 and the enclosure 802. To accomplish the desirableoptical characteristics described hereinabove, UV curable adhesive 232should have approximately the same index of refraction as enclosure 802.This structure has the distinct advantage of minimizing the number ofoptical surfaces wherein a significant mismatch of indices of refractionbetween two different mediums can occur, thus increasing the opticalefficiency of the imaging system and reducing stray light. A suitableoptically clear UV cured adhesive is Norland Optical Adhesive 68manufactured by Norland Products, Inc., of New Brunswick, N.J. Othermaterials suitable for making the image sensor assembly 801 areavailable from Dymax.

The block 802 is completed by attaching the aperture stop 203 to lens202. If the aperture stop is a member, it may be attached to the outersurface of the lens using an adhesive, one or more mechanical fasteners,or the like. If the aperture stop is paint, it may be applied directlyto the surface of the lens element 202 after the lenses 208 and 209 arecovered with a removable mask, such as tape. After the paint dries, themask can be removed. The optical assembly 801 is then mounted to asupport 220. In particular, the image sensor array 201 is physicallymounted on a base substrate 221 by conventional means, and electricallyconnected to circuitry (not shown in FIG. 2 b) by electrical connectorssuch as wire bonds, solder, one or more connectors, or the like. Thebase substrate 221 may for example be a printed circuit board.

The support 220 may be constructed of the same material as the far fieldbaffle 204, or it may be constructed of a different material. The basesubstrate 221 may be omitted if the far field baffle and the imagesensor are mounted directly to either the support 220 or the housing(not shown) that carries the optical sensor assembly. For example, thesupport 220 may be a printed circuit board to which the image sensor 201and the far field baffle are connected. Regardless of whether the basesubstrate is provided, the far field baffle is mounted to the support220 or the housing (not shown) using an adhesive, a snap connector, amechanical fastener, or the like.

An image sensor assembly 901 according to an alternate embodiment isillustrated in FIG. 9. In this embodiment, the image sensor 201 ispackaged using more conventional electronic packaging, such as a ceramicpackage with a glass lid or a clear plastic package, which may forexample be a quad flat pack or a dual-in-line (DIP) package. Thepackaged image sensor 901 is mounted, by suitable conventional meanssuch as by soldering, to printed circuit board 902. An ultraviolet (UV)curable adhesive 905 is then dispensed onto the packaged image sensor901. The adhesive used can be the same adhesive described above withrespect to adhesive 232. The thickness of the UV curable adhesive isdependent on the packaged image sensor 901 type. If the requiredthickness is too great, layers of the UV curable adhesive can be builtup or another material, such as an epoxy layer, can be sandwichedbetween the UV curable adhesives to decrease the thickness of theadhesive layer 905. The epoxy may be the same material described abovewith respect to the enclosure 230, 802. The lens structure 202 isjuxtaposed with the UV curable adhesive 905 and focused in the mannerpreviously described. Finally, the aperture stop 203 is attached to thelens structure 202 using an adhesive (not shown), mechanical fastener orthe like.

In addition to the means described herein above, the lens structure 202may be supported relative to the image sensor by other means, such as amechanical support. Such a structure is disclosed in U.S. Pat. No.6,130,421, entitled IMAGING SYSTEM FOR VEHICLE HEADLAMP CONTROL, filedon Jun. 9, 1998, the disclosure of which is incorporated herein byreference thereto. The same may also be used to position and maintainthe relative relationship between the components of the optical assemblyincluding the aperture stop and the far field baffle. A mechanicalfastening arrangement is disclosed below with respect to FIG. 24.

Mirror Mounted Image Sensor Assembly

As mentioned above, the headlamp dimmer can be advantageously integratedinto a rearview mirror 1000 as illustrated in FIG. 10, wherein the lightsensor assembly 201 is integrated into an automatic dimmingelectrochromic (EC) mirror subassembly 1001, or other variablereflectance mirror assembly. This location provides an unobstructedforward view through a region of the windshield of the vehicle that istypically cleaned by the vehicle's windshield wipers (not shown).Additionally, mounting the image sensor in the mirror assembly permitssharing of circuitry such as the power supply, microcontroller and lightsensors. More specifically, the same ambient light sensor may be used toprovide an ambient light measurement for both the auto-dimming mirrorfunction and the headlamp control function.

Referring to FIG. 10, light sensor assembly 801 is mounted within arearview mirror mount 1003, which is mounted to the vehicle windshield1002. The rearview mirror mount 1003 provides an opaque enclosure forthe image sensor. The infrared filter 206 can be mounted over a hole1007 in the rearview mirror mount 1003, as is shown. Alternatively, thefar field baffle 214 can be used with the infrared filter 206 mountedtherein. If the far field baffle 214 is used, it is mounted to thecircuit board 1008 with the image sensor assembly 202. Regardless ofwhether the far field baffle is used, the circuit board 1008 is mountedto rearview mirror mount 1003 using mounting brackets 1020 and 1021. Themounting brackets may be implemented using any suitable construction,such as metal brackets, plastic brackets which can be formed eitherintegrally with the housing 1003 or as separate components, mechanicalfasteners which engage the circuit board 1008, or the like. The separatebrackets can be attached using an adhesive, metal fasteners or othermechanical fastening means. Image sensor assembly 201 is thus attachedto, and held stationary by, the rearview mirror mount 1003 which issecurely attached to the vehicle windshield or roof by conventionalmeans.

A connector 1005 is connected to circuit board 1008 using a suitablecommercially available circuit board connector (not shown), which inturn is connected to the image sensor 201 through circuit board 1008.The connector 1005 is connected to a main circuit 1015 through a cable1006. The main circuit board is mounted within rearview mirror housing1004 by conventional means. Power and a communication link with thevehicle electrical system, including the headlamps 111 (FIG. 1), areprovided via a vehicle wiring harness 1017 (FIG. 10).

The Electrical System

The image sensor 201 electrically connected to the main circuit board1015 and mounted in the vehicle rearview mirror housing 1004 (FIG. 10)is represented in FIG. 11. The microcontroller 1105 receives imagesignals from the image sensor 201, processes the images, and generatesoutput signals. Although described with reference to a circuit boardmounted in a rearview mirror housing, the circuit board 1105 can bemounted in a vehicle accessory, such as a sun visor, overhead console,center console, dashboard, prismatic rearview mirror, A-pillar, or atany other suitable location in the vehicle. Should the controlledvehicle (100 in FIG. 1) include an electrochromic mirror, the circuitryfor the electrochromic mirror preferably shares the circuit board 1015(FIG. 10) with microprocessor 1105. Thus, the main circuit board 1015 ismounted within the mirror housing 1004. The EC circuitry furtherincludes ambient light sensor 1107 and glare light sensor 1109, whichmay advantageously be digital photodiode light sensors as described inU.S. patent application Ser. No. 09/307,191 entitled PHOTODIODE LIGHTSENSOR, filed Jan. 25, 2000, now U.S. Pat. No. 6,359,274, and U.S.patent application Ser. No. 09/491,192 entitled VEHICLE EQUIPMENTCONTROL WITH SEMICONDUCTOR LIGHT SENSORS, filed May 7, 1999, now U.S.Pat. No. 6,379,013, the disclosures of which are incorporated herein byreference. Microcontroller 1105 uses inputs from ambient light sensor1107 and glare lights sensor 1109 to determine the appropriate state forthe electrochromic mirror element 1102. The mirror is driven by ECmirror drive circuitry 1111, which may be a drive circuit described inU.S. Pat. No. 5,956,012, entitled SERIES DRIVE CIRCUIT, filed by RobertR. Turnbull et al. on Sep. 16, 1997, and PCT Application No.PCT/US97/16946, entitled INDIVIDUAL MIRROR CONTROL SYSTEM, filed byRobert C. Knapp et al. on Sep. 16, 1997; and U.S. patent applicationSer. No. 09/236,969, entitled AUTOMATIC DIMMING MIRROR USINGSEMICONDUCTOR LIGHT SENSOR WITH INTEGRAL CHARGE COLLECTION, filed May 7,1999, by Jon H. Bechtel et al., now abandoned, the disclosures of whichare incorporated herein by reference thereto. Other driver circuits areknown that can be used to drive the EC element 1102. The EC mirror drivecircuit 1111 provides current to the EC element 1102 through signaloutput 1127.

The mirror may communicate with a light control module over a seriallink therebetween in a manner similar to that disclosed incommonly-assigned U.S. patent application Ser. No. 09/368,325, entitled“VEHICLE COMMUNICATION SYSTEM,” filed on Aug. 3, 1999, by Robert C.Knapp et al., now U.S. Pat. No. 6,229,434, the entire disclosure ofwhich is incorporated herein by reference.

The microcontroller 1105 can take advantage of the availability ofsignals (such as vehicle speed) communicated over the vehicle'selectrical bus in making decisions regarding the operation of theheadlamps 111, which are represented by high beams 1131 and low beams1132 in FIG. 11, and the electrochromic mirror 1102. In particular,speed input 1117 provides vehicle speed information to themicrocontroller 1105, from which vehicle speed criteria can be used fordetermining the control state for the headlamps 111. The reverse signal1119 informs microcontroller 1105 that the vehicle is in reverse,responsive to which the microcontroller 1105 clears the electrochromicmirror element 1102 regardless of the signals output from the lightsensors 1107, 1109. Auto ON/OFF switch input 1121 is connected to aswitch having two states to dictate to microcontroller 1105 whether thevehicle headlamps 1131, 1132 should be automatically or manuallycontrolled. The auto ON/OFF switch (not shown) connected to the ON/OFFswitch input 1121 may be incorporated with the headlamp switches thatare traditionally mounted on the vehicle dashboard or incorporated intosteering wheel column levers. Manual dimmer switch input 1123 isconnected to a manually actuated switch (not shown) provides a manualoverride signal for the high beam state. Should the current controlledstate of the high beams be ON, the microcontroller will respond toactuation signal manual override signal control input 1123 to turn thehigh beams OFF temporarily until the driver restores operation or,optionally, until a predetermined time has elapsed. Alternatively,should the high beams be OFF, the microcontroller 1105 will respond toan actuation signal on input 1123 to turn the high beams ON. The manualhigh beam control switch can be implemented using a lever switch locatedon the steering column of controlled vehicle 100 (FIG. 1).

The circuit board 1101 has several outputs. The control signal onelectrochromic output 1127 provides current to the electrochromicelement 1102. Additional outputs (not shown) may optionally be providedto control exterior electrochromic rearview mirrors (not shown) if suchadditional mirrors are provided. The microcontroller 1105 communicatesthe current state of the low beam headlamps 1131 and the high beamheadlamps 1132 to the headlamp drive 1104 via headlamp control output1127. The microcontroller 1105 generates control signals communicatedover conductor 1113 (FIG. 11) to an optional visual indicator 1115 whichdisplays the current state of the high beam headlamps to the driver ofcontrolled vehicle 100. The high beam indicator is traditionally locatedin or near the vehicle's instrument cluster on the vehicle dashboard. Asdescribed further below, a separate indicator may be provided toindicate whether the automatic headlamp control is active. A compasssensor 1135 may be connected to the circuit board 1015 via abi-directional data bus 1137. The compass can be implemented using acommercially available compass of the type generating digital or analogsignals indicative of the vehicle's heading, such as those described inU.S. Pat. No. 5,239,264 entitled ZERO-OFFSET MAGNETOMETER HAVING COILAND CORE SENSOR CONTROLLING PERIOD OF AN OSCILLATOR CIRCUIT; U.S. Pat.No. 4,851,775 entitled DIGITAL COMPASS AND MAGNETOMETER HAVING A SENSORCOIL WOUND ON A HIGH PERMEABILITY ISOTROPIC CORE; U.S. Pat. No.5,878,370 entitled VEHICLE COMPASS SYSTEM WITH VARIABLE RESOLUTION; U.S.Pat. No. 5,761,094, entitled VEHICLE COMPASS SYSTEM; U.S. Pat. No.5,664,335, entitled VEHICLE COMPASS CIRCUIT; U.S. Pat. No. 4,953,305entitled VEHICLE COMPASS WITH AUTOMATIC CONTINUOUS CALIBRATION; U.S.Pat. No. 4,677,381 entitled FLUX-GATE SENSOR ELECTRICAL DRIVE METHOD ANDCIRCUIT; U.S. Pat. No. 4,546,551 entitled ELECTRICAL CONTROL SYSTEM;U.S. Pat. No. 4,425,717 entitled VEHICLE MAGNETIC SENSOR; and U.S. Pat.No. 4,424,631 entitled ELECTRICAL COMPASS, the disclosures of all ofthese patents are hereby incorporated herein by reference. A fog lampcontrol 1141 can be connected to receive via fog light control output1142 control signals generated by microcontroller 1105. Fog lamp control1141 controls front fog lamps 1143 and rear fog light 1145 to turn ONand OFF.

Some or all of the inputs 1117, 1119, 1121, 1123, and 1135, and outputs1127, 1113, 1127, and 1142, as well as any other possible inputs oroutputs, such as a steering wheel input, can optionally be providedthrough a vehicle communications bus 1125 shown in FIG. 11. Vehicle bus1125 may be implemented using any suitable standard communication bus,such as a Controller Area Network (CAN) bus. If vehicle bus 1125 isused, microcontroller 1105 may include a bus controller or the controlinterface may be provided by additional components on the main controlboard 1015.

FIG. 12 illustrates a headlamp drive 1104 including a drive circuit 1203for low beam headlamps 1131 and a drive circuit 1201 for high beamheadlamps 1132. Bus 1127 includes respective wires 1206 and 1207carrying pulse width modulated (PWM) signals generated bymicrocontroller 1105 for driving low beam headlamps 1131 and high beamheadlamps 1132. Alternatively, headlamp drive 1104 may contain a DCpower supply to vary the voltage supplied to the lamps 1131, 1132, andthus their brightness, in response to control signals on output 1127.Yet another alternative envisioned is to vary the aim of the high beamheadlamps 1131 as is described hereinbelow and as taught in U.S. Pat.No. 6,049,171, entitled CONTINUOUSLY VARIABLE HEADLAMP CONTROL, filed byJoseph Stam et al. on Sep. 18, 1998, the disclosure of which isincorporated herein by reference.

Headlamp drive 1104 provides power to the high beam 1131 and low beam1132 headlamps. In the simplest case, the headlamp drive contains relaysengaged in response to signal 1127 to turn ON or OFF the headlamps. In amore preferred embodiment, high beam headlamps 1131 and 1132 fade ON orOFF under the control of headlamp drive 1104 which generates a variablecontrol signal. Such a control system is described in copending U.S.Pat. No. 6,049,171 incorporated herein above by reference thereto. Ingeneral, the patent teaches variable emission control of the headlampscan be provided by energizing the headlamps using a pulse widthmodulation (PWM) supply, wherein the duty cycle of the drive variedbetween 0% and 100% to effect a continuously variable brightness fromthe headlamps 1131, 1132.

The microcontroller 1105 analyzes images acquired by the image sensorassembly 201 responsive to which it detects oncoming or precedingvehicles in the forward field of view. The microcontroller 1105 usesthis information in conjunction with the various other inputs thereto todetermine the current control state for the headlamps 1131, 1132. Thecurrent control state of the headlamps refers to the brightness of thehigh beams and the low beams. In a variable control system, thisbrightness is varied by changing the duty cycle of the beams or the DCvoltage applied to the lamps as described above. In a non-variablesystem, the control state refers to whether the high beams and low beamsare ON or OFF. A more detailed schematic showing the connections to themicrocontroller 1105 is shown in FIG. 13. The microcontroller 1105 canbe implemented using a microcontroller, a microprocessor, a digitalsignal processor, a programmable logic unit, a discrete circuitry, orcombination thereof. Additionally, the microcontroller may beimplemented using more than one microprocessor.

Operation

The combined effect of the lens structure 202 and the far field baffle204 will first be described with respect to FIGS. 2 a and 7. Asmentioned above, in one embodiment, the image array 301 contains 64columns and 80 rows of 30 μm pixels. The forward scene imaged throughthe red lens 209 is located on one region 703 of the image array 301.The forward scene imaged through the other lens element 208 is locatedon region 702 of the image array 301. In the embodiment illustrated,each of these regions is a 60 wide by 20 high pixel subwindow of theimage array. The centers of the two regions 702 and 703 are separated1.2 mm in the Y direction, the same spacing as the center axis of lens208 and 209. Fourteen pixel rows 704 define a band that lies between thetwo regions 702, 703 and serves as a border, or buffer, separating thesetwo regions.

The image sensor assembly 250 provides several advantages. Because theblock will be solid, it eliminates any surfaces between the image sensor201 die and the lens structure 202. By eliminating these surfaces, straylight is reduced. Second, the preferred embodiment allows for the activealignment of the lens, which allows for compensation of variousmanufacturing variances, as is described in greater detail herein above.Finally, the assembly is inexpensive, eliminating the need for costlyceramic packaging. Some or all of the above-mentioned advantages can berealized through variations on this structure. For example, theenclosure 230, UV curable adhesive 232 and possibly the stress relievinggel 805 (FIG. 8) can be replaced with a UV cured epoxy adhesive.

In operation, an image is exposed onto the image array 301 (FIG. 3) foran exposure period, which may also be referred to herein as anintegration period. At the end of the exposure period, an output signalis stored for each of the pixels, and preferably is stored in the pixelsas is the case with the photogate pixel architecture described in U.S.Pat. No. 5,471,515 previously incorporated herein by reference. Theoutput signal from each of the pixels is representative of theillumination sensed by each pixel. This output signal is transferred tothe column output circuitry 302 one row at a time. The column outputcircuitry includes capacitors storing the respective pixel outputsignals for each pixel in the row. Next, the pixel output signals aresuccessively amplified by an analog amplifier 303. The amplifier gain isadvantageously adjustable, and may for example be controlled toselectively increase the amplitude of the amplifier input signal by 1(unity gain) to 15 times, in integer increments. Adjustment of the gainof the amplifier permits adjustment of the system sensitivity. Theamplified analog signals output from amplifier 303 are sampled by aflash analog-to-digital converter (ADC) 404. The flash ADC 404 convertseach of the amplified analog signals, which correspond to respectivepixels, into eight-bit digital gray scale values. Various bias voltagesfor the sensor are generated by digital-to-analog converter (DAC) 105.Two of the voltages generated by the bias generators are the ADC highand low reference values, which determine the analog voltages that willcorrespond to digital values of 255 and 0, respectively, thus settingthe range of the ADC.

Serial timing and control circuitry 309 dictates the timing sequence ofthe sensor operation, and is described in detail in co-pending U.S. Pat.No. 5,990,469, entitled CONTROL CIRCUIT FOR IMAGE ARRAY SENSORS, issuedto Jon H. Bechtel et al on Nov. 23, 1999, the disclosure of which isincorporated herein by reference.

The image sensor control process will now be described beginning withreference to FIG. 14. The control process may include control of anelectrochromic (EC) mirror. However, because processes for controllingan EC mirror are well known, such processes are not completely describedherein. Electrochromic devices are generally known, and examples ofelectrochromic devices and associated circuitry, some of which arecommercially available, are disclosed in Byker U.S. Pat. No. 4,902,108;Bechtel et al. Canadian Patent No. 1,300,945; Bechtel U.S. Pat. No.5,204,778; Byker U.S. Pat. No. 5,280,380; Byker U.S. Pat. No. 5,336,448;Bauer et al. U.S. Pat. No. 5,434,407; Tonar U.S. Pat. No. 5,448,397;Knapp U.S. Pat. No. 5,504,478; Tonar et al. U.S. Pat. No. 5,679,283,Tonar et al. U.S. Pat. No. 5,682,267; Tonar et al. U.S. Pat. No.5,689,370; Tonar et al. U.S. Pat. No. 5,888,431; Bechtel et al. U.S.Pat. No. 5,451,822; U.S. Pat. No. 5,956,012; PCT application Serial No.PCT/US97/16946; and U.S. patent application Ser. No. 09/236,969, nowabandoned, the disclosures of which are incorporated herein by referencethereto.

The forward ambient light sensor 1107 and rear glare sensor 1109 measurethe forward and rear light levels, as indicated in step 1401 (FIG. 14).The forward ambient measurement is used to control both the low beam andhigh beam headlamps 1131, 1132 and the electrochromic mirror 1102.Additionally, the forward ambient measurement may be used to control thebrightness of the daytime running lights and the brightness of the taillights. The rear glare measurement is used for the control of theelectrochromic mirror 1102 reflectivity. The forward ambient light levelmeasurement is averaged with prior measurements to compute a forwardtime averaged ambient light level. This average light level is computedas the average of measurements taken over a 25-30 second interval.Responsive thereto, the microcontroller 1105 computes the control statefor electrochromic element 1105 as a function of the light levelmeasured by sensors 1107 and 1109 in step 1202. Where themicrocontroller 1115 is a microcontroller selected from the MotorolaMCS912, the electrochromic element drive state can be set by programminga pulse width modulated (PWM) duty cycle corresponding to the desiredreflectance level of the electrochromic element into a pulse widthmodulated peripheral to the Motorola MCS912 family microcontroller. ThisPWM output is then fed to a series drive circuit in a manner similar tothat disclosed in U.S. Pat. No. 5,956,012, entitled SERIES DRIVECIRCUIT, filed by Robert R. Turnbull et al. on Sep. 16, 1997. If theheadlamps 1131, 1132 are not in auto mode as determined in step 1403,which is manually set responsive to the signal 1121, the microcontroller1105 returns to step 1401, such that the microcontroller will continueto control the variable reflectance of the electrochromic element 1102.Decision 1403 provides the user with a manual override if the high beamsare ON. Additionally, the high beam automatic control will be skipped instep 1403 (the decision will be NO) if the high beams are not ON.

If it is determined in step 1403 that the automatic mode is active, themicrocontroller 1105 uses the average ambient light level measured instep 1401 to determine whether the ambient light level is below a lowbeam minimum threshold in step 1404. The threshold may for example be1-3 lux, and in one implementation was 2 lux. If the ambient light levelis above the threshold, indicating that high beam headlamps would notprovide significant advantage, high beam control will not be used, andthe microcontroller 1105 returns to step 1401. If the ambient lightlevel is below the low beam minimum, for example below approximately 2lux, the use of high beam headlamps may be desired. In this case, themicrocontroller 1105 will operate to control the headlamps 1131, 1132.In addition to the average ambient light level discussed above, it isalso advantageous to consider the instantaneous ambient light level.Should the instantaneous ambient light level suddenly drop to a very lowvalue, for example less than 0.5 lux, automatic high beam operation maybegin immediately rather than waiting for the average ambient lightlevel to reach the threshold for operation of the high beams. Thissituation may occur when a vehicle sitting under a well lit intersectionsuddenly crosses the intersection into a dark street where high beamoperation is desired immediately. The microcontroller 1105 analyzesimages of the forward scene acquired by image sensor 201 to detect thepresence of oncoming or preceding vehicles as indicated in step 1405.Based upon the results of step 1405, the microcontroller sets thecontrol state of the headlamps in step 1406. Setting the control staterequires setting a duty cycle for the pulse drive in the preferredembodiment. The Motorola MCS912 family microcontroller includestimer/counter peripherals which can be used to generate pulse widthmodulated signals 1206 and 1207. In some vehicles, the low beamheadlamps will always be ON regardless of the state of the high beams.In such a vehicle, only the duty cycle of the high beams will be varied.Other vehicles will have the low beams OFF when the high beams are ON,in which case the duty cycle of the low beams will be reduced as thehigh beam duty cycle is increased. Control of the vehicle headlightsusing a PWM signal is disclosed in U.S. Pat. No. 6,049,171, entitledCONTINUOUSLY VARIABLE HEADLAMP CONTROL, filed by Joseph Stam et al. onSep. 18, 1998, the disclosure of which is incorporated herein byreference.

Step 1405, which is the process of acquiring images in the forward fieldof the vehicle and analyzing such images, is described in greater detailwith reference to FIG. 15. A first pair of images are acquired in step1501 through both the red lens 209 and the cyan lens 208, correspondingto the two fields 702 and 703 shown in FIG. 7. The field of view of theresulting images is approximately 25° horizontally and 15° verticallyusing the 64 by 26 pixels, the lens optics, and the far field baffledescribed above. These images are taken at a low sensitivity.Sensitivity of the image sensor 201 may for example be dictated by theframe exposure time, the analog amplifier gain, and the DAC high and lowreferences. The image sensor should be just sensitive enough to imageoncoming headlamps at the maximum distance for which the controlledvehicle's headlamps should be dimmed. These images will be sufficient todetect oncoming headlamps at any distance of interest and nearby taillamps without being washed out by bright headlamps or other noise lightsources. In this mode, the sensor should not be sensitive enough todetect reflections off signs or reflectors except in rare cases wherethe reflecting object is very near to the controlled vehicle. Duringdark ambient light conditions, this sensitivity will be low enough todetect only lighted objects.

The sensitivity of the image sensor when acquiring the images in step1501 may also be varied according to whether the high beams arecurrently ON. When controlling high beams manually, a driver willtypically wait until an oncoming vehicle 105 (FIG. 1) or a precedingvehicle 110 is almost close enough for the controlled vehicle's highbeams to be annoying before dimming the headlamps 111. However, if thehigh beams are OFF, most drivers will not activate their high beamheadlamps even if an oncoming vehicle 105 is at a great distance. Thisis in anticipation that the oncoming vehicle 105 will soon come within adistance where the controlled vehicle's high beam headlamps will annoythe oncoming driver, such that the driver of the controlled vehicle 100will have to turn the high beams OFF shortly after they were activated.To partially mimic this behavior, a higher sensitivity image is acquiredif the high beams are OFF, enabling detection of vehicles at a greaterdistance, than if the high beams are ON. For example, the image sensorwhen the high beams are OFF can have 50% greater sensitivity than whenthe high beams are ON.

The images are analyzed in step 1502 (FIG. 15) to locate any lightsources captured in the images. In step 1503, the properties of thelight sources detected are analyzed to determine if they are fromoncoming vehicles, preceding vehicles, or other objects. If a lightsource from a preceding vehicle 110 is bright enough to indicate thatthe high beams should be dim, the control process proceeds to step 1510and the high beam state is set.

If no vehicles are detected in step 1503, a second pair of images istaken through lens 208, 209 at a greater sensitivity. First, adetermination of the state of the high beams is made in step 1505. Thisdetermination is made because the sensitivity of the second pair ofimages may be five to ten times the sensitivity of the first pair. Witha higher sensitivity image, more nuisance light sources are likely to beimaged by the image sensor 201. These nuisances are typically caused byreflections off road signs or road reflectors, which become much morepronounced with the high beams ON. When the high beams are ON, it isadvantageous to limit the forward field of view to the area directly infront of the controlled vehicle such that it is unlikely that reflectorsor reflective signs will be in the field of view. An ideal narrowedfield of view is about 13° horizontally, which is achieved by areduction of the width of regions 702 and 703 (FIG. 7) to about 35pixels. If the high beams are OFF, an image with the same field of viewas the low sensitivity images acquired in step 1501 can be used sincethe reflections of low beam headlamps off of signs and reflectors aremuch less bright than those when high beams are used. Thus, the decisionstep 1505 is used to select either a narrow field of view image in step1506 or a wide field of view in step 1507. For either field of view, apair of images will be taken. As described above with respect to theacquisition of low sensitivity images in step 1501, the sensitivity ofthe high sensitivity images may also be varied according to the state ofthe high beam headlamps to provide additional control in avoidingnuisance light sources.

As with the low sensitivity images, the high sensitivity images areanalyzed to detect light sources in step 1508. A determination is madeif any of these light sources represent a vehicle close enough to thecontrolled vehicle to require dimming of the high beam headlamps.

Additional images, with greater sensitivity and/or different fields ofview, may be acquired in addition to those mentioned above. Additionalimages may be necessary depending on the dynamic range of the imagesensor. For example, it may be necessary to acquire a very highsensitivity image with a very narrow field of view to detect a precedingcar's tail lamps at a great distance. Alternatively, should the imagesensor have sufficient dynamic range, only one pair of images at onesensitivity may be needed. It is advantageous to use three sets ofimages, a low sensitivity set, a medium sensitivity set, and a highsensitivity set. The medium sensitivity set has about 5 times thesensitivity of the low gain and the high gain has about 20 times thesensitivity of the low gain. The low gain image set is primarilyutilized for detection of headlamps while the medium and high gainimages are primarily utilized for detection of tail lamps.

Depending on the quantum efficiency of the image sensor at differentwavelengths of light, and the filter characteristics of the filters usedfor the lens elements 208 and 209, it may be advantageous to use adifferent sensitivity for the two regions 702 and 703. The timing andcontrol circuitry 309 described in the U.S. Pat. No. 5,990,469 can beenhanced to provide the capability to acquire two different windows ofpixels simultaneously and use different analog gains for each window.This is accomplished by adding a register which contains the gain valuesfor the analog amplifier used during acquisition of each subwindow. Inthis way, the relative sensitivity of the two regions can beautomatically balanced to provide a similar output when a white lightsource is imaged through both lens elements. This may be of particularadvantage if the image for region 703 is acquired without filtering thelight rays, for example by using a clear lens instead of a cyan filterfor rays passing through lens element 208. For this lens set, the pixelsin region 702 will receive approximately 3 times as much light whenimaging a white light source as those pixels in region 703 which receivelight that has passed through a red filter. The analog gain can be set 3times as high for pixels in red filtered region 703 to balance theoutput between the two regions.

The analysis of images to detect light sources indicated in steps 1502and 1508 is described with reference to FIG. 16. Analysis begins withthe image in region 703 acquired through the red lens. It isadvantageous to begin with the red filtered image because severalnuisance light sources do not admit a significant amount of red light.These nuisance light sources include mercury vapor streetlights, greentraffic lights, and reflections off green and blue highway signs.Therefore, a number of potential nuisance light sources are eliminatedfrom consideration. Pixel locations are referred to by X and Ycoordinates with the 0,0 pixel location corresponding to a top leftpixel. Beginning with the 0,0 pixel 1401 and raster scanning through theimage, each pixel is compared to a minimum threshold in step 1602. Theminimum pixel threshold dictates the faintest objects in the image thatmay be of interest. If the current pixel is below the pixel thresholdand it is not the last pixel in the red image window, as determined instep 1603, analysis proceeds to the next pixel as indicated in step1604. The next pixel location is determined by raster scanning throughthe image by first incrementing the X coordinate and examining pixels tothe right until the last pixel in the row is reached, and thenproceeding to the first pixel in the next row.

If it is determined that the current pixel value is greater than theminimum threshold, a seed fill analysis algorithm is entered in whichstep the size, brightness and other parameters of the identified lightsource are determined as indicated in step 1605. The seed fill algorithmis used to identify the pixels of the image sensor associated with acommon light source, and thus identify associated pixels meeting a pixelcriteria. This can be accomplished by identifying contiguous pixelsexceeding their respective threshold levels. Upon completion of the seedfill algorithm, the properties of the light source are added to thelight source list in step 1606 for later analysis (steps 1503 and 1509in FIG. 15) to determine if certain conditions are met, which conditionsare used to identify whether the light source represents an oncoming orpreceding vehicle. A counter of the number of sources in the list isthen incremented as indicated in step 1607. The microcontroller thengoes to step 1603.

If it is determined in step 1603 that the last pixel in the red imagehas been examined, the microcontroller 1105 determines whether any lightsources were detected, as indicated in step 1608. If no light source isdetected, the analysis of the image terminates as indicated at step1609. If one or more light sources are detected through the red lens209, the cyan or clear image window 702 is analyzed to determine thebrightness of those light sources as imaged through the other lens 208,in order to determine the relative color of the light sources. In thissituation, the “brightness” of the sources refers to the sum of the grayscale values of all the pixels imaging the source; a value computed bythe seed fill algorithm. The first source on the list is analyzed instep 1610. A seed fill algorithm is executed in step 1611, with the cyanimage starting with the pixel having the same coordinates (relative tothe upper left of the window) as the center of the light source detectedin the red image. In this manner, only those pixels identified with alight source viewed through the lens associated with the red filter willbe analyzed as viewed through the other filter, which is advantageous,as many nuisance light sources which would otherwise be analyzed whenviewed through a clear or cyan filter will be removed by the red filter.By only considering light sources identified through the red filter, theamount of memory required to store information associated with lightsources viewed through the other filter will be reduced. The ratio ofthe brightness of the source in the red image 703 to the brightness ofthe source in the other image 702 is stored in the light list, asindicated in step 1612, along with the other parameters computed in step1605 for the current light source. This procedure continues for othersources in the light list 1613 until the red to cyan ratios are computedfor all sources in the list 1615, at which point the analysis terminatesat step 1614.

As a further measure to reduce the required memory, the pixel data maybe processed as it is received without storing the entire image inmemory. Such a processing algorithm is disclosed in commonly assignedU.S. patent application Ser. No. 09/799,310, entitled IMAGE PROCESSINGSYSTEM TO CONTROL VEHICLE HEADLAMPS OR OTHER VEHICLE EQUIPMENT, filed onMar. 5, 2001, by Joseph S. Stam, published as U.S. patent applicationPublication No. 2002/0156559 A1, the entire disclosure of which isincorporated herein by reference.

It will be recognized that where it is desirable to count the number oflight sources to determine the type of driving environment, and inparticular to identify city streets or country roads, it may bedesirable to count all of the light sources viewed through the cyan orclear filter. In this way, nuisance light sources can be counted.Alternatively, the number of light sources viewed through the red filtercan be counted for purposes of inhibiting turning ON the high beams if athreshold number of sources are identified.

The seed fill algorithm used in steps 1605 and 1611 is shown in FIG. 17a. The outer section of the seed fill algorithm is entered with thecurrent pixel value at step 1605. The outer section of the seed fillalgorithm is executed only once at each step 1605, while the innerrecursive seed fill algorithm is entered many times until all contiguouspixels meeting a pixel criteria are identified. After the entry step1701 of the outer section of the seed fill algorithm, several variablesare initiated as indicated in step 1702. The variables XAVG and YAVG areset to zero. These variables will be used to compute the average X and Ycoordinates of the pixels imaging a light source, which averagecoordinates will together correspond to the center of the light source.The TOTALGV variable is used to sum the gray scale values of all thepixels imaging the source. This value will define the brightness of thesource. The SIZE variable is used to tally the total number of pixelsimaging the source. The MAX variable stores the maximum gray scale valueof any pixel imaging the source. A CALLS variable is used to limit thenumber of recursive calls to the recursive inner seed fill function toprevent memory overflow as well as for tracking.

The inner seed fill algorithm is first entered in step 1703. The startof the inner recursive seed fill function for the first and subsequentcalls to the seed fill function is indicated by block 1704. The firststep in the inner seed fill function is to increment the CALLS variableas indicated in step 1705. Next, microcontroller 1105 determines if theCALLS variable is greater than the maximum allowable number of recursivecalls as determined in step 1706. The number of recursive calls islimited by the amount of memory available for storing light sourceinformation. If it is determined that the number of recursive callsexceeds the threshold, the recursive function proceeds to step 1719,wherein the counter is decremented and then returns to the step fromwhich the recursive function was called. Should this occur, a flag isset indicating that the current light source had too many recursivecalls and parameters computed by the seed fill algorithm will beincorrect. This prevents too many levels of recursion from occurring,which would overflow the memory of the microcontroller. It is alsopossible to implement the algorithm non-recursively.

If the decision in step 1706 is that the CALL variable is not greaterthan the maximum allowable, the microcontroller 1105 next compares thecurrent pixel with a minimum gray scale threshold in step 1707 todetermine if the pixel is significantly bright to be included in thelight source. The threshold considered in step 1707 can be constant orvary by position. If it varies, the variable thresholds may be stored ina spatial look-up table having respective pixel thresholds stored foreach pixel, or each region of the image sensor. Where the threshold isvariable by position, it is envisioned that where a pixel at onelocation exceeds its associated pixel threshold, the controller cancontinue to use that threshold for adjacent pixels while searching for acontiguous group of pixels associated with a single light source, or thecontroller can continue to use the respective pixel thresholds stored inthe spatial look-up table.

If the condition in step 1707 is not met, this inner recursive seed fillfunction terminates by advancing to step 1719. If the pixel has a highenough gray scale value as determined in step 1707, its gray scale valueis added to the global TOTALGV variable 1708, its X and Y coordinatesare added to the XAVG and YAVG variables 1709 and 1710, and the sizevariable is incremented in step 1711. If the gray scale value of thepixel is greater than any other pixel encountered in the current seedfill, as determined in step 1712, the MAX value is set to this grayscale value 1713.

Following a no decision in step 1712, the gray scale value of the pixelis set to 0 to prevent further recursive calls from including thispixel. If a future recursive call occurs at this pixel, and the pixel isnot zeroed, the pixel will be added the second time through. By zeroingthe pixel, it will not be added again, as the pixel's gray scale valueis no longer greater than the minimum threshold. Additionally, thispixel will be ignored in step 1602 should it be encountered again whilescanning the image during analysis.

The inner recursive seed fill algorithm next proceeds to recursivelycall to itself until it has looked to the right, left, above and beloweach pixel until all of the contiguous pixels exceeding the minimumpixel threshold value in decision step 1707 are considered. Step 1715represents returning to step 1704 for the pixel to the right. Themicrocontroller will continue to look at pixels to the right until itreaches a pixel that does not meet the criteria of decision step 1706 or1707. Step 1716 represents returning to step 1704 for the pixel to theleft. Step 1717 represents returning to step 1704 to look at the pixelabove. Step 1718 represents returning to step 1704 to look at the pixelbelow. The microcontroller will then look at the pixel to the left ofthe last pixel that did meet decision step 1707. The processor will lookat pixels adjacent each pixel exceeding the threshold of step 1707should the neighboring pixels exist (i.e., the immediate pixel is not anedge pixel). Step 1719 decrements the CALLS variable each time the stepis executed, and the microcontroller will return to the calling programuntil the CALLS value reaches 0. Returning to the function that calledit may be another instance of the inner recursive function, or shouldthis be the initial pixel examined, to the outer recursive algorithm1721.

An example of how the inner and outer seed fill algorithms operate willnow be described with reference to FIG. 17 b. The example is made withrespect to an exemplary very small image sensor having 30 pixels. Pixels4, 9, 10, 11, 14, 15, 16, 17, 18, 21, 22, 23, and 28 exceed thethreshold in step 1707 in this example. Additionally, the number ofcalls required does not exceed the threshold in step 1706. The imagearray 301 is impacted by a light source 1751, indicated by contour 1751.The microcontroller will operate as follows in evaluating the pixels.For pixel 1, the microcontroller 1105 will enter the seed fill algorithmat step 1701, initialize the variables in step 1702, and set the currentpixel in step 1703. The microcontroller will next enter the inner seedfill function in step 1704. The CALLS variable will be incremented to 1in step 1705, which is below the Maximum Calls threshold. Because thereis no light on the pixel, the minimum threshold is not exceeded and themicrocontroller will go to step 1719, decrement the CALLS variable instep 1720, and because this is the first time through the inner seedfill program, the microcontroller will continue to steps 1721-1723. Theprocess will be repeated for pixels 2 and 3, which are both below theminimum pixel threshold used in step 1707.

When the microcontroller gets to pixel 4, it will enter the outer seedfill at step 1701, set the variables to-zero in step 1702, set thecurrent pixel to pixel 4 in step 1703, and enter the inner seed fillalgorithm. The CALLS variable will be incremented to 1, as it is thefirst pixel in this outer seed fill. The CALLS variable will be lessthan the Maximum Calls threshold and the pixel's gray scale value willexceed the minimum threshold. Accordingly, the gray value will be addedto TOTALGV, the pixel coordinates will be added to those that will beconsidered for XAVG and YAVG, and the SIZE will be incremented such thatthe size will be 1. The gray value for pixel 4 will be the MAX, as it isthe only gray value in this outer seed fill. The gray value will be setto zero for pixel 4 in step 1714.

The microcontroller will then identify all of the contiguous pixels thatexceed the threshold set in step 1707. In particular, through the innerseed fill routine disclosed in FIG. 17 a, the microcontroller will addthe pixels as follows. Pixel 4, added first as it is the first with agray scale value greater than the threshold (“the threshold” in thisparagraph referring to the minimum threshold in step 1707). The programthen calls the recursive function for pixel 5 to the right, which is notadded as it is below the threshold (as used in this paragraph, “added”means the pixel's coordinates are added to XAVG and YAVG, the pixel'sgray scale value is added to TOTALGV, SIZE is incremented, and thepixel's gray scale value becomes the maximum pixel gray scale value ifit exceeds MAX). Pixel 3 to the left is called next, and it is not addedfor the same reason. There is no pixel above pixel 4. Accordingly, therecursive function is next called for pixel 10 in step 1718. Pixel 10will be added as its value is greater than the threshold. Themicrocontroller 1105 will then look to the right of pixel 10, namely atpixel 11, which is greater than the threshold, so it will be added. Themicrocontroller will then look to the right of pixel 11, which is pixel12. Pixel 12 will not be added as its gray scale value is below thethreshold. Looking to the left of pixel 11, pixel 10 will not be addedas it was zeroed when it was added previously. Looking above pixel 11,pixel 5 will not be added. Looking below pixel 11, pixel 17 will beadded. Next, the recursive routine will be called for the pixel to theright of pixel 17. Pixel 18 will be added. Moving on to the recursiveroutine for pixel 18, there is no pixel to the right of pixel 18.Looking to the left of pixel 18, pixel 17 will not be added as it waszeroed when it was added. Looking above pixel 18, pixel 12 will not beadded. Looking below pixel 18, pixel 24 will not be added as it is belowthe threshold. Moving back to the previous recursive function that wasnot exhausted, the microcontroller 1105 will move back and look to theleft of pixel 17, which is pixel 16. Pixel 16 is added. Calling therecursive function again, the microcontroller will look to the right ofpixel 16. Pixel 17 will not be added as it was cleared after it waspreviously added. Looking to the left of pixel 16, pixel 15 is added.Calling the recursive function from pixel 15, the microcontroller willlook to the right at pixel 16. Pixel 16 is not added, as it was zeroedafter it was previously added. Looking to the left, pixel 14 is added.Calling the recursive function from pixel 14, the microcontroller willlook to the right at pixel 15, which will not be added. Looking to theleft of pixel 14, pixel 13 is not added. Looking above pixel 14, pixel 8is not added. Looking below pixel 14, pixel 20 is not added. Moving backto the function that called the recursive function for pixel 14, themicrocontroller will look above pixel 15 at pixel 9. Pixel 9 is added.Calling the recursive function for pixel 9, looking to the right, pixel10 is not added. Moving to the left, pixel 8 is not added as it is belowthe threshold. Looking above, pixel 3 is not added. Looking down, pixel15 is not added as it was previously cleared. Moving back to thefunction that called the recursive function for pixel 9 has themicrocontroller looking at the pixel below pixel 15. Pixel 21 is thenadded. Starting the recursive function for pixel 21, looking to theright, pixel 22 is added. Starting the recursive function for pixel 22,pixel 23 is added as it exceeds the threshold. Starting the recursivefunction for pixel 23, pixel 24 is not added as it is below threshold.Moving to the left, pixel 22 is not added as it was zeroed. Lookingabove, pixel 17 is not added as it was zeroed after it was added.Looking down, pixel 29 is not added as it is below the threshold. Movingback to the function that called the recursive function for pixel 23 hasthe microcontroller 1105 looking to the left of pixel 22. Pixel 21 isnot added as it was cleared. Looking above pixel 22, pixel 16 is notadded. Looking below pixel 22, pixel 28 is added. Performing therecursive function for pixel 28, pixel 29 to the right is not added,pixel 27 to the left is not added, pixel 22 above is not added, andthere is no pixel below pixel 28. Moving back one function, therecursive function for pixel 22 was completed, so the microcontrollerreturns to pixel 21. Looking to the left of pixel 21, pixel 20 is notadded. Pixel 15 above pixel 21 is not added and pixel 27 below pixel 21is not added. The recursive function for pixel 15 was exhausted, so themicrocontroller looks above pixel 16 to pixel 10 which is not added.Looking below pixel 16, pixel 22 is not added. Moving back one functionhas the microcontroller looking above pixel 17 at pixel 11, which is notadded. Looking below pixel 17, pixel 23 is not added, if the recursivefunction for pixel 11 was completed, the microcontroller returns to thelast non-exhausted pixel of the contiguous lighted pixels. Themicrocontroller looks to the left of pixel 10, and pixel 9 is not added.The microcontroller looks above pixel 10, and pixel 4 is not added.Looking below, pixel 16 is not added. The inner seed fill is complete.

After the last pixel is added, YAVG, XAVG and size are used to selectthe center of the light in steps 1722 and 1723.

The seed fill scheme just described is the preferred seed fill algorithmfor analysis of the red image 703. It requires some modification for theother image 702. This need can be seen from the following example. Wherea pair of oncoming headlights is identified as two separate lights inthe red image, it is possible that these sources may contain more lightin the cyan half of the spectrum than the red half (as is the case withHigh Intensity Discharge headlamps). In this case, what was detected astwo separate light sources in the red image can bloom into one source inthe cyan image. Thus, there would only be one source in the cyan imageto correspond to two light sources in the red image. After step 1611 iscompleted for the first source in the red image, the bloomed cyan imagepixels would have been cleared in step 1714, such that they would not beavailable for the analysis of the second light source in the red image.Thus, after the source in the cyan image is determined to correspond tothe first source in the red image, there would be no source on the cyanimage to correspond to the second source in the red image. To preventthis, it is useful to preserve the image memory for the cyan imagerather than setting the gray scale value to zero as in step 1714 so thatthe bloomed source is detected as corresponding to both of the sourcesin the red image.

Since the red image has already been processed, the memory that storedthe red image can be used as a map to indicate which pixels in the cyanimage have already been processed. All pixels in the red image memorywill have been set to gray scale values less than the minimum thresholdas a result of the processing. The pixels that were identified as lightsources where zeroed whereas the light sources that were not clearedwill have some low gray scale value. This characteristic can be used toset the pixels in the red image memory to serve as markers forprocessing pixels in the cyan image. In particular, when the seed fillalgorithm is executed for the cyan image, step 1714 is replaced by astep that sets the value of the pixel in the red image memorycorresponding to the currently analyzed cyan pixel to a marker value.This marker value could be, for example, 255 minus the index of thecurrent light source in the light list. The number 255 is the largestvalue that can be stored for a gray scale value. In this way, there willbe a unique marker stored in the red image memory for pixels analyzedeach time step 1611 is executed for a light on the list. In addition tothe above change to step 1714, a test must be added after step 1707 todetermine if the value of the pixel stored in the red image memorycorresponding to the currently analyzed pixel is equal to the markervalue for the current light source index, indicating that this pixel hasalready been recursively visited, in which case the microcontrollerwould go to step 1719.

Steps 1501 and 1502 for the red image in region 703 and correspondingsteps 1506, 1507 and 1508 for the other image in region 702, have nowbeen explained in detail. In step 1503 and 1509, the light source listis analyzed to determine if any of the identified light sources indicatethe presence of an oncoming or proceeding vehicle. FIG. 18 is a flowdiagram of the series of tests applied to the information gathered oneach light source in the light list during the previous analysis stepsto determine the type of light source. The tests in FIG. 18 are appliedto each source in the list independently.

First, a check is made to see if the recursive seed fill analysis ofthis light source exceeded the maximum number of subsequent recursivecalls allowed as determined in step 1801. If so, the light source islabeled an extremely bright light in step 1803 since the number ofpixels in the source must be large to cause a large number of subsequentrecursive calls. Next, the TOTALGV variable is compared to avery-bright-light-threshold 1802. If TOTALGV exceeds this threshold, thelight is also labeled as extremely bright in step 1803.

If neither of the conditions 1801 or 1802 are met, the light source isanalyzed to determine if it has a 60 Hz alternating current (AC)intensity component, indicating that the light source is powered by anAC source, in step 1804, to distinguish it from vehicles which arepowered by DC sources. Many streetlights, such as high-pressure sodiumand mercury vapor lights, can be effectively distinguished from vehicleheadlamps in this way. To detect the AC component, a series of eight 3×3pixel images are acquired at 480 frames per second, for example. The 3×3pixel window is centered on the center of the light source beinginvestigated. The sums of the nine pixels in each of the 8 frames arestored as eight values. These eight values represent the brightness ofthe source at ¼ cycle intervals over two cycles. The magnitude of the 60Hz Fourier series component of these eight samples can be computed bythe following formula:AC=(A ² +B ²)^(1/2)A=1.0*(F 1−FMIN)+(−1.0)*(F 3−FMIN)+1.0*(F 5−FMIN)+(−1.0)*(F 7−FMIN)B=1.0*(F 0−FMIN)+(−1.0)*(F 2−FMIN)+1.0*(F 4−FMIN)+(−1.0)*(F 6−FMIN)where F1 to F7 refer to the eight summed gray scale values of each ofeight frames and FMIN refers to the minimum value of F1 through F7. Thevalue AC is divided by the mean gray scale value of F1 to F8 to give theAC component of interest in step 1804. The scheme is of particularconvenience since the sampling rate is exactly four times the frequencyof modulation analyzed. If this were not the case, the coefficients foreach of F1 through F7 would have to be changed to accommodate this.Additionally, if the system were to be used in countries were the ACpower is not at a 60 Hz frequency, the sampling rate or coefficientswould be adjusted.

While the AC detection scheme is described for only one window, it isadvantageous to perform the above analysis by imaging the source throughboth the cyan and red filters, or the red and clear filters, and thenusing the maximum computed AC component from the two sample sets todetermine the AC component for step 1804. This allows for accuratemeasurement of sources that have either strong short or long wavelengthcomponents in their spectrum. If the light source AC component isgreater than the minimum threshold as determined in step 1805, the lightsource is determined to be an AC source as indicated in step 1806.Additional measures may be taken to aid in distinguishing between suchnuisance light sources and headlamps, such as to provide a lower ACcomponent threshold for an upper area of the sensed image, whileproviding a higher threshold for the mid to lower right hand side and anintermediate threshold for the mid to lower left hand side.

The next step is to distinguish light sources which are reflections offroad signs or other large objects. Road signs are large compared to thesize of the headlamp or tail lamp. As a result, they tend to be imagedonto many more pixels than a vehicle lamp, unless the lamp is so brightas to bloom in the image. Sign reflection sources may have a largenumber of pixels, indicated by the SIZE variable, but a lower averagegray scale value than vehicle lamps which have a much higher intensity.If the SIZE variable exceeds a given size threshold as determined instep 1807, the average gray scale value (TOTALGV/SIZE) is comparedagainst an average pixel level threshold, which is the maximum signaverage gray scale value, in step 1808. If the average gray scale valueis less than this threshold, the light source is determined to be areflection off a sign as indicated in step 1809.

An additional check for yellow signs, which typically occurs in thefront of the vehicle when turning through a curved road, is to measurethe color of bright objects and determine if they are likely yellow.Even when using the low gain image, the reflection off a nearby sign maysaturate several pixels in both subwindows and make relative colordiscrimination difficult. However, the same high-speed images acquiredwhen performing an AC validation can be used to accurately determine therelative color even for bright images. This is accomplished by lookingat the average value of the F1 through F7 frames mentioned hereinabovethrough each lens. The ratio of the average of the F1 to F7 framesviewed through the red lens to the average of the F1 through F7 framesviewed through the cyan or clear lens is computed. This ratio will behigher for yellow signs than for white lights but not as high as fortail lamps. If this ratio is within a certain range indicating that itis likely a yellow sign, this object can be ignored or the threshold fordimming for this object can be decreased, allowing only extremely brightyellow objects to dim the high beams. By allowing the system to respondto bright yellow objects by dimming the high beams, the headlight dimmerwill respond to a light source in the event that a headlamp ismisdiagnosed as a yellow sign.

Once potential nuisance sources are filtered out, the light source canbe identified as a headlamp or a tail lamp. The red to cyan ratiocomputed in step 1612 is used to determine if the source has sufficientred component to be classified as a tail lamp in step 1810. If thisratio is lower than a tail lamp redness threshold, control proceeds tostep 1811, where the threshold for consideration as a headlamp isdetermined. This threshold can be determined in a number of ways, butthe most convenient method is to use a two dimensional look-up table ifthe microcontroller has sufficient read-only memory (ROM) to accommodatethe table, as is the case with the Motorola MCS912 family ofmicrocontrollers exemplified herein.

The center of the light source is used as the index into the look-uptable to determine the threshold. The look-up tables are created toprovide different thresholds for different regions of the field of view.For example, the thresholds for regions of the field of view directly infront of the vehicle are lower than those used for regions off to theside. The look-up table can be optimized for the particular vehicle'shigh beam emission pattern to determine how annoying the high beams willbe to oncoming and preceding traffic at various angles. Ideally, thelook-up table used when the vehicle's high beams are activated isdifferent than when they are not. When high beams are off, thethresholds to the side of the vehicle can be lower than they are whenhigh beams are activated. This will prevent the high beams from comingON when there is a vehicle in front of, but off at an angle to, thecontrolled vehicle, such as happens when on a curve on an expressway.Also, different lookup tables are used for high and low sensitivityimages for much of the same reasons. In fact, the lookup tables mayindicate that for certain regions, or all regions of the field of viewin high sensitivity image, headlamps be ignored completely. A highsensitivity image is only analyzed if the low sensitivity did not detectoncoming or preceding vehicles, so non-red light sources in a highsensitivity image are most likely very distant headlamps or nuisancesources. Therefore, the high sensitivity images may only be analyzed forred sources.

In step 1812, the TOTALGV variable, which is the total pixel level, iscompared to the threshold total pixel level for headlights as determinedfrom the appropriate look-up table. If this variable is greater than thethreshold, the value is compared to the threshold multiplied by a brightmultiplier in step 1813. If TOTALGV is greater than this value, thelight source is determined to be a bright headlamp in step 1815. If notthe light source is a headlamp as indicated in step 1814. The need todistinguish between headlamps and bright headlamps will become clearerin the discussion of the control state of the headlamps. As analternative to comparing TOTALGV to a threshold times a brightmultiplier, yet another look-up table can be provided to dictatethresholds for bright headlamps.

A procedure similar to that just described is performed in step 1816 ifthe light source is determined to be red. A series of lookup tables areprovided for tail light thresholds and the appropriate lookup table isused to determine the threshold for the given light source location. In1817, the total pixel level for tail light threshold is compared to theTOTALGV variable to determine to light sources bright enough to be ofinterest. If so, the light source is labeled as a tail light in step1819. If not, the light source is ignored in step 1820.

Should the cyan lens element 301 be replaced by a clear lens, adifferent ratio threshold is used in step 1810. In this case, a redlight will have approximately the same brightness in both images, but awhite or other color light will be substantially brighter when imagedthrough the clear lens. This ratio is determined based on the analoggain settings for both the red and cyan (or clear) images.

Once the images of the forward field have been acquired and analyzed instep 1405, the state of the headlamps must be determined in step 1406.This is best described by considering a state machine implemented in themicrocontroller 1105, which state machine is illustrated in FIG. 19. Inthe following example it is assumed that headlamp drive 902 is a pulsewidth modulator drive and the high beam brightness can be varied bychanging the duty cycle of the pulse width modulator drive. It is alsoassumed that the low beam headlamps remain on at 100% duty cycle at alltimes. Each of the states in FIG. 19 represents a control state of thehigh beam headlamps. The duty cycle of the high beam headlamps is set tothe value indicated by the current control state. The distribution ofthe duty cycles amongst the control states is non-linear to compensatefor the fact that headlamp brightness is a non-linear function of dutycycle and to provide the appearance of a constant percent change fromcycle to cycle. Also, there are several states for both 0% and 100% dutycycle, indicating that several states must be traversed before theheadlamps begin to go ON or OFF, providing a time delay verificationinsuring that the detected light source is persistent over severalimages. The number of states is exemplary only, and those skilled of theart will recognize that it may vary depending on the desired fade ON andOFF rate of the high beams and time between cycles. Additionally, thebright light indicator (which is typically located on the vehicle'sdashboard) fades ON as the state moves from state 11 to state 14. Thebright light indicator fades OFF as the states move from state 7 tostate 4. This provides some hysteresis to avoid flashing the indicatorON and OFF. Alternatively, if the indicator does not fade ON and OFF,the state at which the bright light indicator turns ON will preferablybe a higher state than the state at which the bright light indicatorturns OFF. In either case, hysterisis is provided for the headlampcontrol.

After each control cycle, the headlamp control state can remain the sameor move to a different state. The rules for moving between states aredescribed with reference to FIG. 20. First, if any of the lights in thelight list were determined to have been extremely bright lights in step2001, the current control state is immediately set to a 0 state in step2002. This behavior allows bypass of the fade out feature and rapidresponse to the sudden appearance of headlamps in the forward field ofview, such as happens when driving over a hill. Step 2003 determineswhether a headlamp or tail lamp was detected in the light source list.If not, control proceeds to step 2004, wherein it is determined whetherthe previous state was decremented in the last control cycle.

One of the advantages of the variable beam configuration is the abilityto fade in and out high beams. If a reflection from a sign or reflectoris misdiagnosed as a vehicle lamp, the high beams will begin to dim.When they do, the reflected source will no longer be present in theimage and the high beams will fade back on, likely without bothering thedriver. To prevent rapid oscillation between increasing and decreasingheadlamp beam brightness, the control state must rest in the currentstate for one cycle before changing direction. Therefore, step 2004considers the action during the previous cycle and the system willremain in the current state as indicated in step 2005 if the previousaction was to decrement states.

If the action during the previous cycle was not to decrement states,vehicle speed is considered next in step 2006. If a vehicle is stoppedat an intersection, it will annoy the driver if the high beams come ON,dim with a passing car, and then come ON again. To prevent this, thehigh beams are prevented from coming ON if a vehicle is traveling belowa certain speed, for example 20-mph. A decrease in speed below theminimum speed threshold will not necessarily cause the high beams to dimunless there is an oncoming or preceding car present. Alternatively, thehigh beams can be configured to fade OFF every time the vehicle comes toa stop and then fade ON again once the vehicle begins moving, providedno other vehicles are present. In step 2007, the number of lights in thelight list (counted in step 1607) is checked as an indication of whetherthe driver is driving in city conditions. If there are a large number oflights in the forward field of view, the high beams will not be turnedON. The number of the lights that are alternating current sources mayalso be considered.

If the criteria of steps 2004, 2006, and 2007 are met, the currentcontrol state is incremented one state in step 2008. If this actionresults in the current control state exceeding state 12 as determined instep 2009, the current control state is set to 15 in step 2010 forcingseveral time verification states before the beams can be dimmed again.

Should the microcontroller 1105 detect a headlamp or tail lamp in step2003, the microcontroller determines whether a bright headlamp wasdetected in step 2011. If not, the prior cycle action is considered instep 2012 to prevent rapid oscillation between incrementing anddecrementing to avoid rapid ongoing oscillations between states. If theprior action was not to increment, the current control state isdecremented by 1 state in step 2014. If the new control state is belowstate 3, as determined in step 2015, the current control state is set to0 in step 2016.

Finally, if a bright headlamp is detected in step 2011, it is desirableto more rapidly fade out the high beams by decrementing 2 states in step2018, provided the previous action was not to increment in step 2017, inwhich case the current state is decremented only one state.

A large number of variations of the scheme just described are possible.For example, more states can be added to increase or decrease the timeit takes to fade the high beams in and out. The number of requiredstates will depend upon the image acquisition and analysis cycle time.Ideally, the fade in/out period is about one to two seconds. Anotheralternative is to decrement states as a function of the brightest lightsource detected in the light list rather than to decrement a singlestate for every cycle. In this way, the brightness of the high beam isadjusted as a function of the distance of an oncoming or precedingvehicle rather than just fading in and out. This is particularlyadvantageous where the control mechanism is to vary the beam angle ofthe high beams rather than the intensity of the beams. Yet anotheralternative is to decrement states as a function of the current speed ofthe controlled vehicle. The rate at which states are decremented couldincrease at high vehicle speeds, since oncoming cars will overtake thecontrolled vehicle at a more rapid rate. Yet another alternative is todecrement states as a vehicle slows down. This would allow the highbeams to fade out as a vehicle comes to a stop: a feature that may bedesirable for some drivers. Finally, it should be noted that the use ofdiscrete states is only exemplary. The intensity and/or aim of the highbeam headlamps can be controlled by continuum of values from fully ON tofully OFF.

The previous discussions described in detail the operation of one cycleof the headlamp dimmer control sequence. This sequence is repeatedindefinitely as long as the device is on.

Depending on the time to complete one cycle, the above procedure may beinterrupted to acquire rear glare sensor measurements for theelectrochromic mirror. Additionally, the driver may interrupt the abovesequence by activating the manual high beam switch generating inputsignal 1123 (FIG. 11). This feature is necessary to allow the driver tooverride improper behavior of the control system or to use the highbeams to alert other drivers through flashing the high beams.

Some additional features may be provided with the above-describedhardware and software configuration. One such feature is daytime runninglights (DRLs). On some vehicles, DRLs are provided by operating the highbeams at a reduced intensity. By using the PWM drive circuitry provided,the high beams can be set to a reduced intensity during daylightconditions. The ambient light sensor 1107 can be used to determinedaylight conditions and switch the headlamps to normal low beamoperation at dusk. In particular, the ambient light level can have oneor more light level thresholds associated therewith. When the ambientlight level is a daytime one threshold, the daytime running lights willbe ON. Below that threshold, but above another lower threshold, the lowbeams can be ON. Below that lower bright activate ambient light levelthreshold, the high beams may be operated automatically if the driverdoes not manually disable high beam operation.

Even without the use of DRLs, it is desirable to have automaticactivation of the low beam headlamps at dusk. This control can beprovided by the use of the ambient light sensor 1107. For betterperformance, an additional light sensor can be provided which senseslight from a direction upwards rather than looking straightforward asthe ambient light sensor 1107 does. Such a sky sensor arrangement isdisclosed in U.S. patent application Ser. No. 09/491,192, entitledVEHICLE EQUIPMENT CONTROL WITH SEMICONDUCTOR LIGHT SENSORS, filed by JonBechtel et al. on Jan. 25, 2000, now U.S. Pat. No. 6,379,013, the entiredisclosure of which is incorporated herein by reference. Alternatively,a few rows of pixels in the image sensor can be used to image a regionof the sky above the horizon. An imaging system disclosing such anarrangement is described in U.S. Pat. No. 6,130,421, the disclosure ofwhich is incorporated herein above by reference. The ability to imagethrough both the red and cyan filters can help to distinguish betweenclear and overcast conditions and to detect a sunset.

It is envisioned that the system can detect a tunnel using the imagesensor and a sky sensor. In particular, a potential tunnel condition isdetected when a large area of contiguous dark pixels is detected thatmeets a size threshold level and is located in the center of the image,under daytime ambient light conditions. If the dark area grows while theambient light conditions continue to sense day ambient light conditions,the potential tunnel condition will continue. If the image sensorcontinues to see a large dark area forward of the vehicle when thedaylight ambient conditions are no longer detected, the vehicle will bedetermined to be in a tunnel, and the headlights will be ON. Theheadlights will remain on until the daylight ambient conditions aredetected, at which time the headlights will be turned OFF and daylightrunning lights will be turned ON if the controlled vehicle has daytimerunning lights.

Speed Varying Thresholds

The speed input 1117 can be used in additional ways by microcontroller1115. For example, when driving on an expressway, it is necessary todetect oncoming cars in the opposite lane, which is usually separated bya median. Therefore, the microcontroller must be more sensitive tooncoming headlamps at larger angles than would be necessary forback-road driving where there is no median separating oncoming traffic.Incorporating a wide field of view for back-road driving has thedisadvantage of increasing the likelihood that the image sensor willdetect house lights, which are typically incandescent. Incandescentlight sources will not be filtered by the AC rejection algorithm. Suchhouse lights are not typically present on the side of the freeway. Byincreasing the sensitivity of the device to objects at higher angleswhen the vehicle is traveling at higher speeds, such as speeds in excessof 50 to 60 mph, the system will be able to sense cross-median trafficon expressways without increased sensitivity to house lights on backroads. It is envisioned that the field of view could be increased whenthe vehicle speed exceeds 65 mph and decreased when the vehicle speedpasses below 60 mph.

In particular, it is envisioned that prior to step 1601, additionalsteps can be provided to make the field of view speed sensitive. Thesesteps are illustrated in FIG. 21. The vehicle speed is input in step2101. The microcontroller determines in step 2103 whether the status iscurrently a wide view for expressway driving. If it is not, themicrocontroller 1105 determines whether the speed is greater than 55mph. If not, the status does not change. If the vehicle speed isdetermined to be greater than 55 mph in step 2105, the field of view ofthe image sensor 201 is increased as indicated in step 2107. The fieldof view in the horizontal direction can be increased by 30 to 150percent, and advantageously 60 to 125 percent, relative to the narrowerfield of view at lower speeds. If it was determined in step 2101 thatthe controlled vehicle 100 is in the expressway state, themicrocontroller 1105 determines in step 2109 whether the vehicle speedhas dropped below 45 mph. If it has, the microcontroller reduces thefield of view of image sensor 201 to its narrower non-expressway fieldof view. In one advantageous embodiment, the field of view remains thesame at all speeds but the thresholds for responding to lights at higherangles are decreased as speed increases. This is advantageous because itallows detection of very bright objects at high angles when the vehicleis traveling at slow speeds, but it is not sensitive to less brightobjects, such as house lights or street signs, when traveling at slowspeeds. In particular, at high speeds reducing the thresholds increasesthe sensitivity to cross-median traffic. The thresholds are reduced moresignificantly to the left than to the right since cross median trafficis to the left. This property can be reversed for left-hand-drivecountries.

It is envisioned that the field of view will be varied by increasing anddecreasing the width of the pixels used by the image sensor in themanner described above when the high beams are ON or OFF.

According to another aspect of the invention, the integration time forthe pixels of the image array sensor can be increased at higher speeds.This increase in integration period increases the sensitivity of theimage array sensor. The system is thus able to detect an oncomingvehicle sooner. This may be particularly advantageous, as oncoming carsare likely to be traveling faster when the controlled vehicle istraveling faster. Accordingly, providing the light control system with ahigher sensitivity to shorten the response time will better emulate adesired dimming characteristic of the headlamps by dimming the headlampsat a desired vehicle distance. To provide this function, in step 2107the microcontroller 1105 increases the sensitivity and/or widens thehorizontal viewing angle, whereas in step 2111, the microcontrollerdecreases the sensitivity and/or narrows the horizontal viewing angle.

It is further envisioned that adjustments can be made to the thresholdin step 1707 as a function of speed. Such a system can be implementedusing a look-up table stored in read only memory. FIG. 22 illustratesregions of the image sensor array 301, with the regions radiatingoutwardly from the center. The regions may not be symmetrical sinceoncoming traffic usually occurs more to the left and signs and nuisancelight sources are more likely to the right in right side drivecountries. The look-up table sets a respective threshold for each of theregions 1-6 with the regions having sequentially, incrementally greaterthresholds moving outwardly from the center. Thus the center region 1will have the lowest threshold and the outer peripheral 6 will have thehighest threshold. In addition, the thresholds at different angles willvary as a function of speed, such that at higher speeds, the thresholdswill be lower in regions 3 through 5 than they will be at higher speeds.For example, where two fields of view are provided, one table willcontain respective thresholds for pixels in the regions for lower speedsand another table will contain respective thresholds in regions for thehigher speeds. Each table will assign an integration time and/orthresholds for use in analyzing different portions of the field of view.Because the greater the distance from the center the greater the viewingangle of the scene image, lowering the threshold in the outer regionsincreases the system's responsiveness to light sources at wider anglesto the controlled vehicle.

Either the thresholds or the integration times for the pixel sensors ofthe image array, or both the thresholds and the integration times, canbe changed to increase the sensitivity of the sensor at differentspeeds. Thus, it is envisioned that the field of view can be the same atboth high and low speeds. However, the thresholds or the sensitivity(i.e., the integration period or the amplifier gain) can be altered suchthat at low speeds images viewed at wide angles will have little impacton the dimming decision whereas at high speeds the images viewed at wideangles will have substantially more impact on the dimming decision athigh speeds. It is further envisioned that instead of using look-uptables, an algorithm can be used to alter the sensitivity of the lightsensor as a function of the angle of the image being viewed. Such analgorithm can be used to reduce the memory requirements for the systemat the expense of requiring greater processing power to implement thefunction.

Turning

As indicated above, it is disadvantageous to have a wide field of viewwhen traveling slowly, such as occurs when traveling on back roads.However, when turning, it is necessary to have a wide field of view sothat the image sensor can detect other vehicles that will come in frontof the controlled vehicle prior to the controlled vehicle's headlampsstriking the other vehicle. It may also be desirable to lower thethresholds for those regions of the sensed image in the direction of theturn. A subroutine that the microcontroller 1105 uses for changing theviewing angle of the image sensor is disclosed in FIG. 23. It isenvisioned that the subroutine will be executed each time a turncondition is initiated. For example, the microcontroller may detect anyone or more of the following: activation of a vehicle turn signal aloneor in combination with braking; a change in vehicle heading detected bythe compass; global positioning information; and change in direction ofthe vehicle steering wheel or front tires. Responsive to such an event,the microcontroller 1105 will input the criteria to be used in making adecision as to whether the field of view needs to be altered. Forexample, a compass input, an input from a turn signal, globalpositioning system (GPS) receiver information, wheel turn indicationfrom the vehicle steering system, vehicle speed, gyroscope output, tirespeed sensors of an anti-lock brake system (ABS), or a combination ofthese inputs may be input in step 2301. Additionally, motion analysis(discussed below) may be used to sense turning of the vehicle.

In step 2303, the microcontroller 1105 will determine whether thecriteria input in step 2301 indicate that the field of view should bealtered. For example, when the vehicle turn signal is ON, and thevehicle is slowing down, the viewing angle sensitivity can be altered inthe direction of the turn signal. Alternatively, actuation of thevehicle brake system in combination with a change in vehicle headinggreater than a threshold angle of change could trigger a change insensor viewing angle. In particular, the compass sensor information canbe compared to a threshold change of direction to determine if thecontrolled vehicle 100 is turning, and responsive thereto themicrocontroller 1105 can increase the sensitivity of the image sensor201 and associated circuitry to light sources in the direction that thevehicle is turning. In order to implement such a turning control, thecompass must generate vehicle heading information that themicrocontroller can use. Commercially available compasses of the typeused in vehicles generate an output, which will operate within 2° to 3°of accuracy as the vehicle turns. As a consequence, the rate at whichthe vehicle heading is changing and the direction that the vehicle isturning can be determined from the compass output or GPS information. Inone embodiment, a compass is integrated into an electrochromic mirrorwith an automatic headlamp dimmer and the compass sensor signal isutilized to enhance the performance of the automatic headlamp dimmer.

If it is determined in step 2303 that a shift of the sensitivity patternis required, the image sensor will shift its sensitivity as indicated instep 2305. For example, the high sensitivity region 1 of the imagesensor will generally be in the center of the array such that lightsstraightforward of the vehicle will have the strongest impact on thelight control process. This is particularly advantageous as thebrightest light produced by the controlled vehicle illuminates straightout in front of the controlled vehicle. As the controlled vehicle turns,the center axis of each of the regions 1 through 5 will shift asindicated in step 2305. As a consequence, these regions shift in thedirection that the vehicle is turning such that they are centered to theright or left instead of being centered on the Y axis (FIG. 22). Thesensitivity of the pixels in array 301 will thus shift right as thevehicle turns right, and shift left as the vehicle turns left. Thedegree that the sensitivity field shifts can vary depending upon therate of change of the vehicle as well as the speed of the vehicle.

It is envisioned that the sensitivity can be changed using the lookuptable. In particular the lookup table can contain respective integrationperiods and thresholds according to the location of pixels such that thesensitivity is as shown in FIG. 22 when the vehicle is travelingstraight. As the vehicle turns, the addresses associated with columns ofpixels may be altered such that the integration periods and thresholdsfor pixels in the column will shift left or right.

If the change is not sufficient to change the sensitivity, as determinedin step 2303, the microcontroller will determine in step 2307 if thevehicle is going straight. The microcontroller will continue to monitorthe rate of change of the vehicle heading until the vehicle is headinggenerally straight, as indicated in step 2307. It will be recognizedthat subroutine may be run once as an interrupt routine such that othersubroutines may be run in between execution of routine 2300.

It is further envisioned that adjustments may be made in the verticaldirection, in addition to the horizontal direction, for example if achange in vehicle inclination is detected.

Light List History

Information about lights from previous frames can be useful inevaluating current frames. However, there is typically insufficientmemory in low cost microcontrollers to store previous frames so as toretain a complete history of each frame's content. To minimize thememory requirements for implementing the system, while retaining someuseful historical information, the brightness and location of one ormore of the brightest lights detected in one or more previous frames arestored for use when processing a later frame. The entire light list froma previous frame need not be stored, unless significant memory isavailable. It is also useful to store the brightness and location ofonly the brightest lights detected in one or more preceding frames. Thisinformation can be used to provide fast return to bright. After anoncoming car 105 has passed the controlled vehicle 100, it is useful toreturn to the high beam state as soon as possible. The night vision ofthe driver in the controlled vehicle may be temporarily impaired by thelights of the oncoming vehicle. The impact of this loss of night visionmay be minimized by providing as much scene illumination as possible, assoon as possible, following passage of a vehicle. The microcontroller1105 uses the light list history information to implement a fastreturn-to-bright. In particular, after step 2007 in FIG. 20, themicrocontroller 1105 can determine whether the current frame is suddenlyclear of bright light sources following a preceding frame that containeda very bright headlamp. In such a case, it is likely that the brightheadlamp has just passed the controlled vehicle. If this situationoccurs, the normal gradual, delayed fade-in period can be bypassed, orpartially bypassed, and the high beams can be incremented by more thanone state, such as by eight states (FIG. 19), to return to bright highbeams more quickly.

Another scenario where the opposite result is desired occurs when thecontrolled vehicle comes up behind a preceding vehicle 110. As thecontrolled vehicle 100 approaches the preceding vehicle 110, the imagesensor will detect the preceding vehicle's tail lights and dim thecontrolled vehicle's high beams responsive thereto. When the controlledvehicle moves to the side to drive around the slower preceding vehicle,the tail lights of the preceding vehicle will move out of the field ofview of the image sensor. However, if the controlled vehicle's brightlights are activated, they will shine into the eyes of the driver of thevehicle being passed via the exterior rearview mirror. This isparticularly problematic when the controlled vehicle is passing a truck,as it may take a long time to pass the truck. In this situation, themicrocontroller can include a decision step following step 2007 todetermine whether the previous frame included a tail light, and if so,to set a predetermined delay before the high beam headlamps can beactivated. Where the high beam lights are dimmed responsive to precedingtail lights, a long delay will thus be introduced before turning thehigh beams back ON. For example, the high beams may come on severalseconds after the tail lights move out of the scene being imaged. Motionanalysis (described below) may be used to determine the rate ofovertaking a preceding vehicle or the rate at which a preceding vehiclemay drive out of range to thereby enable additional control over theheadlamps.

The light history can also be used to select an integration period forthe image array sensor pixels. In particular, it is envisioned that theamplifier gain 303 for the pixels can have different gains or differentintegration intervals to increase the dynamic range of the light sensor.For example, three different gains or integration periods could besupported. A bright light will saturate all but the lowest gain, whereasa dim light such as a tail light can not be detected at a low gain. Thelight history can be used to remember that the sensor was washed outeven at low gain, and an ultra low sensitivity can be used to detectlights.

Another use for the light list history is determining traffic density.In particular, the traffic density can be ascertained from the timeperiod count between detecting oncoming headlights. Thus, in or near acity where traffic is heavier, the system can respond to that conditionby having a relatively long delay period. On the other hand, wheretraffic is light, such that oncoming traffic is less likely, the delayto turn on the bright lights can be short. It is envisioned that as thetraffic increases, the return-to-bright time period will lengthen,whereas as the traffic decreases, the return-to-bright period willshorten. It is further envisioned that a number of different criteriacould be used, such as the number of frames since a vehicle waspreviously detected or the percentage of time that the bright lightswere on over a predetermined sampling period. In these ways, the numberof objects detected over time can be used in the control of theheadlamps, and in particular, to at least partially inhibit turning onthe high beams.

It is envisioned that where a vehicle includes an electrochromic mirrorglare sensor to detect light from the rear of the vehicle, or any otherdevice having a rearward directed optical sensor, such as a rear visionsystem, additional information can be accessed which is useful forcontrolling the return-to-bright interval. In particular, when thebright headlights are dimmed because of tail lights from a precedingvehicle, the headlights can return to bright a predetermined time afterthe tail lights disappear from in front of the vehicle or whenheadlights are detected by the rear glare sensor in the rearview mirror,whichever occurs first. Where headlights from a trailing vehicle aredetected immediately prior to the disappearance of tail lights from apreceding vehicle, the use of the rearward sensor for detecting a returnto bright condition will be precluded. Additional considerations can beused in making the return-to-bright decision. For example, a minimum anda maximum interval can be required before return-to-bright.

It is envisioned that the system will only provide a variablereturn-to-bright interval under certain conditions, such that thereturn-to-bright interval will typically be a default time interval.However, a fast return-to-bright interval will occur following acondition where really bright headlights are detected and thendisappear, as such bright lights will reduce the driver's night vision.Additionally, a slow return to bright condition would be used followingdisappearance of a preceding tail light since the driver's vision willnot have been impaired and it is desirable to avoid shinning the highbeams into the eyes of a vehicle being passed.

It is further envisioned that integration periods in the current framemay be adjusted based upon measurements made in a previous frame. Inparticular, an extremely short integration period can be used for theimage sensor 301 where the lowest sensitivity measurements in a previousframe resulted in saturation of the light sensor. To the other extreme,where the previous frame's most sensitive measurements did result indetection of tail lights, a very long integration interval can be usedfor the image sensor 301 to look for tail lights in the current frame.Thus where three integration periods are typically used, two additionalintegration periods can be selectively used when the conditionsnecessitate either an extremely short or long integration interval.

Another use of the light list history is to distinguish signs andreflectors based on the movement of the objects in the image over time.Over a sequence of frames, reflectors and signs will typically move morerapidly toward a side of the image than will vehicles travelinggenerally in parallel with the controlled vehicle. Object lists may becreated as the images are captured as disclosed above and in commonlyassigned U.S. patent application Ser. No. 09/799,310, entitled IMAGEPROCESSING SYSTEM TO CONTROL VEHICLE HEADLAMPS OR OTHER VEHICLEEQUIPMENT, filed on Mar. 5, 2001, by Joseph Stam et al., published asU.S. patent application Publication No. 2002/0156559 A1, the entiredisclosure of which is incorporated herein by reference. The objectlists created may be stored in memory from frame to frame to determinethe behavior of a particular object in the image over time. Forinstance, reflections from signs or other stationary objects can beidentified by the motion of this object in subsequent frames. Flashingoverhead stop or caution lamps can be identified by their rate offlashing. After each frame is analyzed, the object least created fromthis frame is kept in memory and light lists from new frames are storedin a different location. The techniques disclosed in U.S. patentapplication Ser. No. 09/799,310 greatly reduce the amount of memoryrequired for image analysis by not requiring an entire frame to bestored. Therefore, it is practical to store the object lists fromseveral subsequent frames in the amount of memory typically provided inlow cost controllers. The number of object lists stored from previousframes depends on the available memory. As few as one previous objectlist can greatly assist in identifying the motion of an object.

To facilitate tracking of objects over time, additional properties ofobjects can be added as entries into the object list. For a headlampcontrol application, an object list entry may contain:

X Center X coordinate of the center of the object Y Center Y coordinateof the center of the object Total GV Sum of all the gray scale values ofall pixels in the object Size Total number of pixels in the object MaxThe gray scale value of the brightest pixel Redness Brightness ratiobetween the clear and the red images for this object PrevFrameIndexIndex of a light in a previous frame which is the same light as this one(if any) Gain Which image in the cycle; high, medium, or low gain VectorThe direction in which the light is traveling

The total number of objects that can be stored depends upon theavailable memory. For example, the list above would require 9 bytes perentry. If, for example, 500 bytes of memory are available, 50 objectscould be tracked. The object list memory may be allocated as acontiguous array of object entries. Pointers indicate the start of theobject lists for the current frame and previous frames. The newestobjects identified replace the oldest objects in the list.

The objects in the new object list are then compared to the objects inthe previous object list to determine if any of the new objects are thesame as previous objects. A comparison is made by determining if the Xand Y center of an object in the current list is within a radius of acertain number of pixels from an object in the previous list. The radiusthreshold is determined by calculating the maximum amount an object canreasonably move in an image from frame to frame. This number is afunction of the resolution of the sensor and may also be a function ofthe vehicle speed and turn rate. It is possible for two lights in thecurrent list to be daughters of the same light in the previous list.This may occur as a vehicle approaches from a distance and the twoheadlamps, which before were imaged as one blob, become separated in theimage.

Once an object in a previous light list is determined to be the sameobject as in the current light list, a motion vector can be computed toquantify the rate and direction of motion of the object. Motiondetection can be used to distinguish between signs and reflectors,street lights, and vehicles. As illustrated in FIG. 39, the headlights3901 of oncoming vehicles tend to move down and to the left of the imageover a sequence of frames, while signs and reflectors 3903 tend to movedown and to the right. Overhead street lights 3905 tend to move upward.While other techniques are disclosed herein for distinguishing betweenthese objects, motion detection can further increase the accuracy atwhich the system is able to make such distinctions.

Further, such motion detection can be used to distinguish betweenheadlights and tail lights of vehicles and thereby further enhancedistinction that is otherwise based on color analysis.

FIG. 40 shows a functional block diagram of one embodiment of thepresent invention. As shown, the system 4000 includes an image sensor201, a lens 202, a previous light list(s) 4001, and an image processingroutine (seed fill) 4003, which receives data from image sensor 201 andaccesses previous light list(s) 4001 to generate a new light list 4005.New light list 4005 includes information from which various parametersincluding the brightness 4007, position 4009, size 4011, color 4013, ACcomponent 4015, and motion 4017 of each object may be derived. Thesystem 4000 further includes decision rules 4020 that control theexterior vehicle lights including the low beam headlamps 4021 and thehigh-beam headlamps 4023 by adjusting their activation state,brightness, aim, and/or focus to vary the illumination pattern producedthereby. Decision rules 4020 may control the exterior lights as afunction of any one or combination of parameters 4007-4017 as well asambient light levels 4025, vehicle turn rate 4027, vehicle speed 4029,and the state of user actuated switches 4031 (as discussed furtherbelow). Decision rules 4020 may be implemented in a logic circuit (i.e.,microcomputer), a fuzzy logic circuit, or a neural network.

An example of how decision rules 4020 may use more than one parameter tocontrol the exterior lights is to reduce the perceived brightness orotherwise modify the glare area of the present beam illumination patternwhen a nearby headlamp is detected. Decision rules 4020 may determinethat a nearby headlamp is present when the detected headlamp has highbrightness and a relatively high amount of motion. A distant headlamp,on the other hand, would have low brightness and a relatively low amountof amount of motion. A sign would have a low level of brightness buthave a relatively high amount of motion.

Automatic Aim Calibration

Variations in the orientation of the image array sensor relative to thewindshield angle may result in variations in aim of the sensor, whichmay negatively impact the performance of the dimmer. These variationscan be calibrated out over time using a maximum bound placed on theexpected variation in mounting. In general, on straight roads, distantoncoming headlamps will be coming from directly ahead of the opticalsensor system 102. The calibration system uses faint headlamps detectednear the center of the image, and preferably only those within a centerwindow corresponding to the expected mounting variations. Such headlampsmeeting certain criteria will have their position averaged with otherfaint headlamps meeting the same criteria. Over time, this average ofthese lights should correspond to the center of the field of view. Thisaverage value can be used to offset the image window relative to the Xand Y-axis in FIG. 22.

More particularly, in order to detect a flat straight road, from which amisalignment of the optical sensor system can be detected, a variety ofdifferent orientation inputs can be used. The speed of the vehicle maybe required to remain in a certain range between 35 to 50 mph. Thevehicle can be determined to be traveling straight using the compass,GPS, or monitoring the operation of the vehicle steering system. If theheading changes during the test, the measurement will be considered tobe in error. If the vehicle has equipment for providing an elevationmeasurement, any changes in the vehicle's elevation during thecalibration process will result in an error. The elevation measurementmay thus be used in determining whether to adjust the field of view.

A distant vehicle is initially detected by sensing white light near thecenter of the image, which is faint at the highest sensitivity (longestintegration period) of the image sensor. As this light gets brighter,the system monitors the orientation inputs to detect whether the roadcontinues to be flat and straight. If it remains flat and straight for aperiod of time which is at least twice the time period required for thevehicles 100, 105 to pass, the measurement will be valid. The centerpoint detected initially will then be averaged with previous validmeasurements, and the average measurement will be considered to be thecenter of the image. This will be the average X and Y coordinates, whichtogether will mark the center of the image sensor. This location can besaved in EEPROM or flash ROM.

Another method of aiming calibration is to take a very high gain imageand look for the reflection of the road. The average point where thisreflection occurs can be used to calibrate the aim.

Liquid Crystal Filter

An alternative optical system may include a liquid crystal filter 2405that can be used to selectively provide both a red and a blue filter,whereby red and blue images may be viewed by an image sensor 2401through a single lens structure 2403. In such a structure, the imagesensor 2401 need only have one imaging area (e.g., array area 702instead of array areas 702 and 703 as required with two lenses). Thefilter 2405 is implemented using a liquid crystal colored light switch2503 (FIG. 25) electrically connected to microcontroller 1105 throughconductors 2413 and 2411. The filter includes a neutral polarizer 2501,a liquid crystal shutter 2503, a red polarizer 2505, and a bluepolarizer 2507. The neutral polarizer 2501 and red polarizer 2505 areoriented with their polarizing axis aligned in one direction and theblue polarizer 2507 is oriented with its polarizing axis orientedorthogonally to the red and neutral polarizer. The liquid crystalshutter 2503 is implemented using a twisted neumatic (TN) liquid crystalshutter selectively energized under the control of microcontroller 1105.In particular, when the shutter is not energized, the liquid crystaldevice transmits the red light. When the liquid crystal is energized,the liquid crystal device transmits blue light.

It is thus possible to measure the relative intensities of two colors oflight using a single photo sensor or image area. In the unenergizedstate all visible light is polarized in the horizontal direction by theneutral polarizer, rotated 90° by the unenergized TN liquid crystal cellto the vertical direction, and then all but the red light will beabsorbed by the horizontal red polarizer. The red light will then passthrough the vertical blue polarizer. In the energized state all visiblelight will be polarized in the horizontal direction by the horizontalneutral polarizer, and not rotated by the energized TN liquid crystalcell, all visible light will be transmitted by the horizontal redpolarizer and all but blue light will be absorbed by the vertical bluepolarizer. The liquid crystal device can be used as a high-speed lightswitch to alternate between transmission of blue light and red light.The relative intensities of the red and blue light components of anobject or light source can then be determined. Alternatively, a greenpolarizer can be substituted for either the red or blue polarizer toswitch between transmission of blue and green or red and green lightrespectively. Furthermore, a clear polarizer can be substituted for theblue polarizer to switch between red and clear.

Windshield Wiper

To improve dimmer performance when it is raining, it is useful tosynchronize the acquisition of images with the windshield wipers. Forexample, a signal can be provided from the wiper motors to indicate theposition of the wipers. Immediately after the wiper passes over thesensor, and image can be taken to look for cars. Most importantly, it isnecessary to avoid taking images while the wiper is over the imagesensor 301.

Where the controlled vehicle 100 includes a moisture sensor, themoisture sensor can monitor the windshield wiper. A moisture sensorproviding such information is disclosed in U.S. Pat. No. 5,923,027,entitled MOISTURE SENSOR AND WINDSHIELD FOG DETECTOR, issued to JosephStam et al. on Jul. 13, 1999, the disclosure of which is incorporatedherein by reference.

Information regarding the on/off status of the windshield wipers mayalso be used to control the vehicle headlamps. When the headlampcontroller determines that the windshield wipers have been turned on,the headlamp controller may turn on the low beam headlamps of thevehicle assuming they are not already on. In addition, the headlampcontroller may disable the headlamps from operation in a high beam statewhen the vehicle windshield wipers are activated. This may beaccomplished by simply maintaining the headlamps in the low beam statewhen in an automatic control state or otherwise deactivating theautomatic control state such that the high beams may not automaticallybe turned on while the wipers are activated. Additionally, the headlampcontroller could disable any manual activation of the high beams so longas the windshield wipers are turned on. Also, foul weather lights,particularly the fog lights, may be automatically activated when thewipers are on.

The headlamp controller may receive a signal over the vehicle bus fromthe windshield wiper controller indicating that the windshield wipersare activated. Alternatively, the headlamp controller may determine thatthe windshield wipers are activated upon detecting a wiper within thescene imaged by the imaging system. As yet another alternative, theheadlamp controller may receive a signal from a rain sensor that is usedto control the windshield wipers indicating that a control signal hasbeen transmitted to activate the windshield wipers.

Deceleration

In addition to varying the image sensor operation depending upon thevehicle speed, other speed criteria can be used to control the operationof the vehicle headlamps. Turning on the high beams may be inhibitedwhen the vehicle is decelerating, when the brakes are actuated, or whenthe vehicle is traveling slowly. This prevents high beams from coming onwhen coasting to a stop or approaching an intersection. Deceleration canbe detected from the speed input to the microcontroller 1105 (FIG. 11).

Bad Pixel Calibration

An image sensor may contain one or more bad pixels. These bad pixels maymanifest themselves as extremely sensitive pixels, which may cause“white-spots” in the image. Such “white-spots” will cause false lightdetection in the image if the sensor is not calibrated to remove themfrom calculations. During production tests, the location of these whitespots can be measured and stored in a programmable memory associatedwith microcontroller 1105. To compensate for such bad pixels duringnormal operation of the image array sensor, after an image is acquired,the pixel value at the white-spot location may be replaced with theaverage value of its neighboring pixels.

It is possible that a white-spot may form during use of the imagesensor, such that it is not detected during production tests. Such asituation will cause the device to be inoperable. To avoid this problem,it is desirable to calibrate the white-spot out of the image afterrecognizing the bad pixel. In order to detect the white spot, it isnecessary to detect that the pixel remains “lit-up” in several images,and preferably over an extended period of time. A bad pixel will standout if it is repeatedly lit-up when neighboring pixels are dark. Whensuch a pixel is detected, it can be added to the list of bad pixels.

It is envisioned that bad pixels can be periodically tested to determineif their performance has improved. This can be accomplished bymonitoring a sequence of images to determine whether the center pixel isdark while the adjoining pixels are not dark.

“Picket Fence”

In controlling the vehicle headlamps, it is desirable to avoid acondition where the headlamp high beams flash ON and OFF at a relativelyrapid rate, this is particularly important if non-variable two-stateheadlamps are used. For example, a sign along the road can causeflashing of the headlights between bright and normal levels. This occurswhen reflections of the bright high beams from a sign are bright enoughto cause dimming of the high beams and reflections of headlight lowbeams are low enough that the bright high beams are turned ON. Thecondition can be avoided by having the system look at the object thatcaused the high beams to turn OFF. When this condition occurs, the lightlevel at that position is ignored while the pixels around the object arenot ignored for a predetermined number of cycles, such as ten cycles.The length of time that the object is ignored can be variable as afunction of the vehicle's speed. The higher the vehicle's speed, theshorter the period that the object will be ignored. During the timeperiod, the lights will be controlled using pixels other than thoseassociated with the object being ignored.

A reflector can be distinguished from an active source of light byflashing the vehicle headlights off. The time period that the headlightsare off is so short that the image sensor can sense the loss of lighteven though the human eye will not perceive, or barely perceive, thatthe lights were off. A light emitting diode headlamp describedhereinbelow can be turned OFF and ON very rapidly, such that it will beoff for such a short period of time. In operation, the microcontroller1105 controls the headlamp high or low beams to turn OFF, and controlsthe image sensor to image the scene during that brief time period thatthe headlamps are off. The off time period may for example be 10 ms.

Fog Detector

It is desirable for the vehicle to reliably detect a foggy condition,and in response thereto, to automatically turn ON or OFF front and rearfog lamps. Effective fog detectors have not been available heretofore.Fog may be detected by using the image sensor and optical system for theheadlight ON/OFF and headlight dimmer control. Fog can be detected by areduced scene contrast along with scene ambient light leveldeterminations. The ambient light can be determined from the mean grayscale value of the pixels imaging the forward scene or by a separateambient light sensor, such as the ambient light sensor used for theelectrochromic mirror. It is envisioned that the mean can be a clippedmean value. The variance of the gray scale values of the pixels providesa measure of the contrast in the image. Alternatively, the variance canbe determined from the standard deviation of the pixels, and inparticular, when the standard deviation is less than a standarddeviation threshold level, the presence of fog is identified responsiveto which the fog lights can be turned ON. Alternatively, the individualdifferences between the average pixel level and each individual pixellevel can be added for the entire image sensor, and when this totalvariance exceeds a variance threshold level, the presence of fog isdetected. Either of these examples of fog criteria can be used as ameasure of contrast.

Several additional factors may also be considered. The contrast valuemay be an average contrast value over several images. The contrast maybe determined in row-wise fashion to determine the level of fog. Variousregions of the scene may be considered independently. If two colorlenses are present as in the headlamp dimmer, color information may beused. The actual values of the brightness/contrast ratios and the properimage sensor exposure times should be determined experimentally. Thedevice can be set to only operate between a predetermined range ofbrightness levels, such that if the ambient level is too high or toolow, the fog detector will not operate, and manual override will berequired. The ambient light conditions for fog may for example bebetween 1 and 1000 lux. Both the image sensor and the ambient lightsensor can be used to detect fog. If the ambient light level detected bythe ambient light sensor is within the appropriate range, an image ofthe forward scene is acquired with a sensitivity set to the average grayscale value of the pixels (e.g., 128 lux). If the contrast at a givenbrightness level is below a predetermined threshold level, it isdetermined that fog is present.

Snow and Fog Detector

It is also desirable for a vehicle to detect when it is snowing.Typically, in heavy snow conditions, it is not desirable to activate thehigh beams. Further, even if it is not snowing heavily, the snow mayreflect the light from the high beams in such a way that the headlampcontroller mistakenly perceives an oncoming vehicle based upon thereflected light from the controlled vehicle's own headlamps.

To detect snowfall, it is preferable to provide a sensing system thatsenses light levels forward and above the vehicle. To obtain the lightlevel above the vehicle, a separate light sensor may be positioned tosense light from the sky above the vehicle. Such a sky sensor mayinclude a single pixel sensor positioned at a 45° angle relative to thesensor used to sense light forward of the vehicle. The sensor used tosense light forward of the vehicle may be a single pixel sensor or theimage array sensor used to image the scene forward of the vehicle forheadlamp control. The values sensed by the forward and sky sensor may beaveraged over a period of time. Theses sensors may be constructed inaccordance with the teachings of U.S. patent application Ser. No.09/307,191, entitled PHOTODIODE LIGHT SENSOR, filed on May 7, 1999 byRobert H. Nixon et al., now U.S. Pat. No. 6,359,274, and U.S. patentapplication Ser. No. 09/491,192, entitled VEHICLE EQUIPMENT CONTROL WITHSEMICONDUCTOR LIGHT SENSORS, filed on Jan. 25, 2000, by Jon H. Bechtelet al., now U.S. Pat. No. 6,379,013, the entire disclosures of which areincorporated herein by reference.

The controller is coupled to receive the output of both the forwardsensor and the sky sensor and compares the relative brightness in frontof the vehicle with that above the vehicle. In some conditions, it maybe desirable to compare the relative brightness as the brightness of thevehicle's headlights increases. The headlamp controller determines thatit is snowing or foggy when a ratio of the relative brightness forwardof the vehicle to that above the vehicle reaches a threshold as thebrightness of the vehicle's headlights increases due to the reflectionof the headlamp light off the snow in the forward scene.

When the controller determines that snow is falling, it may activate thelow beam headlamps if they are not already activated and can disable thehigh beams from being activated either through automatic control ormanually. Further, automatic control may be disabled and foul weatherlights may be activated. Additionally, the brightness of the vehicle'stail lights and/or brake lights may be increased to increase thevisibility of the vehicle to other rearward vehicles.

The headlamp controller may also infer that the conditions outside ofthe vehicle are snowy or foggy when the driver turns the frontwindshield defroster fan to full speed. In such an event, the controllermay also disable the headlamps from operation in a high beam state andmay disable further automatic control.

The techniques described in this section are particularly well-suitedfor detecting fog at night, while the techniques described in thepreceding section is better suited for detecting fog during daytime.

Daytime Running Light and Tail Light Control

As discussed above, daytime running lights (DRLs) are provided on somevehicles. As also discussed above, DRLs are provided by operating thehigh beams at a reduced intensity by changing the PWM drive signaldelivered to the high beams during daylight conditions. For thispurpose, an ambient light sensor 1107 can be used to determine daylightconditions and switch the headlamps to DRL operation when daylight isdetected.

The controller may also utilize the sensed ambient light level to turnon the low beams when it is sufficiently dark. Additional the DRLs maybe controlled to vary their intensity during daylight conditions.Ambient light levels may vary considerably from the brightest ofdaylight conditions to the conditions existing just prior to activationof the low beam headlamps at dusk. There have been complaints about thebrightness of DRLs when the ambient light levels are relatively dark. Inthe brightest conditions, however, the DRLs are less bothersome becausethey appear to be less bright relative to the ambient light levelssurrounding the vehicle. Accordingly, the headlamp control circuit maybe configured to vary the brightness of the DRLs in response to theambient light levels sensed by an ambient light sensor. Specifically,the control circuit may increase the brightness of the DRLs in responseto increasing ambient brightness.

A similar problem exists with respect to a vehicle's tail lights andbrake lights. Tail lights and brake lights preferably have brightnesslevels that are sufficient to allow drivers to the rear of thecontrolled vehicle to easily determine whether the tail lights and brakelights are on or off regardless of the ambient light level. On the otherhand, at nighttime, tail lights and brake lights can be too bright so asto adversely affect the night vision of drivers to the rear of thevehicle. Accordingly, it is preferable to decrease the intensity of taillights and brake lights with decreasing ambient light levels. Suchintensity variation may be continuous or accomplished in discrete steps.Additionally, it may be desirable to increase the intensity of the taillights and/or brake lights when foul weather, such as rain, fog, orsnow, is detected.

User Control and Feedback

An alternative embodiment of the present invention is shown in FIG. 34.The same reference numerals are used to illustrate common elements as inthe embodiment shown in FIG. 1. Like the embodiment shown in FIG. 11,this alternative embodiment shown in FIG. 34 includes an image sensorchip 201 and a lens 202 preferably mounted in a mirror mount 1003. Acompass sensor 1135 is also preferably mounted in mirror mount 1003. Thecompass sensor may alternatively be mounted in mirror body 1000. Amicrocontroller 1105 is preferably mounted in mirror body 1000 and iscoupled to image sensor chip 201 and compass sensor 1135. Mirror body1000 may further include an electrochromic element 1102 and a compassdisplay 3404, both of which may be controlled by microcontroller 1105.

A forward-facing ambient light sensor 1107 and a rearward-facing glaresensor 1109 are also preferably provided in mirror body 1000.Additionally, a sky sensor 3402 may be provided in mirror housing 1000,which is inclined at an angle to view the scene of the sky above andslightly in front of the vehicle. Such a sky sensor 3402 may be used fordetecting snow or other ambient light conditions. Sky sensor 3402 may bea single pixel sensor or may optionally be incorporated in the mirrormount as an optical element that images a view of the sky onto adesignated area of the image sensor chip. Such a structure is disclosedin commonly assigned U.S. Pat. No. 6,130,421. The disclosures of theabove-mentioned patent and patent application are incorporated herein byreference.

Microcontroller 1105 is coupled to the vehicle bus 3406 for exchange ofvarious information and control signals. As indicated, a switch controlmodule 3408 may be coupled to the bus for providing the states ofvarious switches that may be manipulated by the user to microcontroller1105. For example, a high/low beam switch 3410 may be coupled to switchcontrol module 3408, as may be a headlamp on/off switch 3412. Suchswitches are common in vehicles with the high/low beam switch typicallybeing mounted to the steering wheel column and the headlamp on/offswitch being positioned on the vehicle instrument panel.

The present invention also provides for a user sensitivity selectionswitch 3414 that is coupled to switch control module 3408 to allow auser to adjust the sensitivity of the headlamp control system.Microcontroller 1105 may respond to changes in the sensitivity settingset by the user by adjusting the thresholds that the microcontrollerutilizes to compare to detected light sources to determine when to turnoff or on or fade in or out the high beams. Alternatively,microcontroller 1105 may utilize the sensitivity setting to change therate at which it changes headlamp brightness states or may change theduty cycles associated with those states. Further still, microcontroller1105 may adjust the sensitivity by changing the integration time of someor all of the pixels in the CMOS image array sensor. Also, thesensitivity to light in various portions of the scene in front of thevehicle may be adjusted by varying the thresholds/integration times forpixels in the image array sensor that image the peripheral regions ofthe forward scene. Other adjustments may also be programmed intomicrocontroller 1105 to determine how it should respond to adjustment ofa user-sensitivity switch 3414.

As will be explained further below, the present invention also providesfor the inclusion of an automatic headlamp control on/off switch 3415 bywhich a user may disable the automatic control of the vehicle headlamps.

Also coupled to vehicle bus 3406 is a lighting control module (or bodycontroller) 3416, which controls the state and possibly the perceivedbrightness of the low beam headlamps 3418, the high beam headlamps 3420,and the brightness of the tail lights 3422. Front control module 3416may also be used to control the on/off status or perceived brightness offog lamps. As mentioned above, the brightness of daytime running lightsmay be adjusted by controlling the perceived brightness of high beams3420.

FIG. 35 shows a state diagram for operation of microcontroller 1105 inresponse to various states of the switches coupled to switch controlmodule 3408. As illustrated, the microcontroller 1105 may operate in anautomatic mode or a manual mode in response to the activation of theautomatic control on/off switch 3415. Such a switch may be provided onthe steering wheel column and integrated into the same column switchthat is utilized to manually activate the high beams. For example, ifsuch a column switch is in a middle position, microcontroller 1105 willoperate in a manual mode. If, for example, this column switch is movedto a forward position, microcontroller 1105 will respond by entering anautomatic control mode. As discussed above, during an automatic controlmode, microcontroller 1105 varies the headlamp state between a high beamon state 3502 and a high beam off state 3504 based upon the lightsources detected by the image sensor or upon other events. In the manualmode, however, the headlamps are operated manually in a conventionalmanner. For example, the high beams may initially be in an off state3508 and be turned on by manual toggling of the column switch or othermechanism such that the high beams are in an on state (3510). Toggling aswitch back would turn the high beams off. If the column switch includesa flash-to-pass feature, flashing the column switch would temporarilyturn the high beams (on state 3512) whereas when the user releases thecolumn switch, the high beams are turned off and returned to state 3508.

FIG. 36 shows a state diagram showing a more complex control scheme. Aswith the control scheme shown in FIG. 35, microcontroller 1105 mayoperate in either an automatic mode or a manual mode. Transition betweenthe automatic or manual modes is generally manually selected using aswitch 3415 that may, for example, be provided on the steering wheelcolumn or on the vehicle instrument panel. In the manual mode,microcontroller 1105 operates in the same manner as described above withrespect to FIG. 35. In the automatic mode, however, microcontroller 1105initially operates in an automatic high beam control state 3602 wherebythe high beams are automatically controlled to transition between on andoff states, as well as states of intermediate brightness if theheadlamps are capable of this feature. When operating in the automaticmode in accordance with the scheme shown in FIG. 36, when a user togglesthe column switch 3410 for manually turning on the high beams,microcontroller 1105 turns on the high beams in a manual override state3604 until such time that the user again toggles the column switch, atwhich point microcontroller 1105 returns to the automatic high beamcontrol state 3602. In the event that the user manually activates theflash-to-pass column switch, microcontroller 1105 enters the high beamon flash-to-pass state 3606 and remains in this state so long as theflash column switch remains in the flash-to-pass position. Once the userreleases the flash-to-pass column switch, microcontroller 1105 returnsto the automatic high beam control state 3602.

While the high beams may be activated in their brightest state duringthe flash-to-pass state, it will be appreciated that, according to oneembodiment of the present invention, the brightness of the headlampsduring a flash-to-pass state may be less than full brightness.Specifically, the brightness of the headlamps during a flash-to-passstate may be varied as a function of the sensed ambient light level andalso as a function of the current brightness level of the headlamps. Inthis manner, any time the flash-to-pass switch is actuated, theperceived brightness of the headlamps will be increased by apredetermined increment above that of their current brightness level soas to provide a perceivable increase in the brightness of the headlampsto any preceding vehicles, but without causing a sudden and excessiveglare in the eyes of the drivers of such vehicles.

FIG. 37 shows yet another state diagram for a more complex controlscheme. Again, microcontroller 1105 operates in either an automatic or amanual mode. When in the manual mode, microcontroller 1105 allows theheadlamps to be controlled in the same manner as discussed above withrespect to FIGS. 35 and 36. Again, operation in either the automatic orthe manual mode may be manually selected by the user by manipulation ofa switch 3415.

When in the automatic mode, microcontroller 1105 operates in anautomatic high beam control state whereby the control state variesbetween a high beam on state 3702 and a high beam off state 3704.Microcontroller 1105 moves between states 3702 and 3704 in the mannerdiscussed above responsive to the light sources detected by the imagesensor. When microcontroller 1105 is operating in an automatic mode withthe high beams on (state 3702) and then the column switch 3410 istoggled, microcontroller 1105 will interpret the toggling of the columnswitch as a request to turn the high beams off. Microcontroller 1105thus enters a high beam off manual override state 3708. Microcontroller1105 will maintain the high beams in their off manual override state3708 for a predetermined time period, such as 30 seconds or until thecolumn switch is again toggled. When the time period expires,microcontroller 1105 will initially maintain their high beams in the offstate, but will move to state 3704 whereby the high beams may beautomatically turned back on based upon the automatic headlamp controlalgorithm that is responsive to the light sources detected by the imagesensor. If microcontroller 1105 is in the high beam off manual overridestate 3708 and the column switch is again toggled, microcontroller 1105will interpret this action as a request by the user to move to a highbeam on manual override state 3706. Microcontroller 1105 will maintainthis manual override high beam on state 3706 for a predetermined timeperiod, such as 15 seconds, or until the column switch is again toggled.If the column switch is again toggled, microcontroller 1105 will move tothe high beam off manual override state 3708. Microcontroller 1105 willleave state 3076 and will enter state 3702 when the timer expires so asto initially maintain the high beams in their on status but allow forthe automatic control algorithm to dim or turn off the headlamps inresponse to light sources detected by the image sensor.

If microcontroller 1105 is operating in the automatic control state withthe high beams off (state 3704) and the column switch is toggled,microcontroller 1105 will interpret this as a command to enter the highbeam on override state 3706. Microcontroller 1105 will then leave thehigh beam on manual override state 3706 based on the criteria discussedabove.

If microcontroller 1105 is operating in the automatic control state withthe high beams off (state 3704) and the user manually activates theflash-to-pass column switch, microcontroller 1105 will move to state3710 by which the high beams are turned on in a flash-to-pass state. Thehigh beams will remain on so long as the user holds the column switch inthe flash-to-pass position. Once the user releases the flash-to-passcolumn switch, microcontroller 1105 will return to the automatic modewith the high beams off (state 3704). If the microcontroller is in theautomatic control states with the high beams already on (state 3702), atsuch time that the user activates the flash-to-pass column switch, thehigh beams will remain on in state 3710 so long as the user holds thecolumn switch in the flash-to-pass position. However, once the userreleases the column switch, microcontroller 1105 returns to state 3704rather than state 3702 so as to turn the high beams off. If conditionswarrant, headlamp controller 1105 will turn the high beams back on underautomatic control.

Other features that may be implemented would allow the automaticheadlamp controller to gradually fade the brightness of the headlamps atsuch time that the headlamp switch 3412 is turned to an off position orif the vehicle ignition is turned off. Alternatively, the headlampcontroller may fade the headlamps a designated time after it is detectedthat all occupants (or just the driver) have exited the vehicle. Suchfading provides the benefits of illuminating the area in which thevehicle occupants will exit the vehicle. By fading the lights in thismanner, rather than leaving the lights on in their full brightnessstates for a fixed time period, it is less likely an observer wouldsuggest to the driver or other occupants that they had left theirvehicle lights on since that observer would be able to see the fading ofthe headlamps during such time period.

Referring back to FIG. 34, an instrument control panel module 3424 maybe coupled to vehicle bus 3402. An indicator 3426 may be coupled toinstrument panel control module 3424 so as to receive control signalsfrom microcontroller 1105 over vehicle bus 3406. Typically, vehicleshave had a single indicator, often a blue light, which is activated whenthe vehicle's high beams are in an on state. Such single indicator,however, does not provide a user with any feedback as to the relativebrightness of the high beams when they are controlled automatically by aheadlamp controller to have various intermediate brightness levels. Toprovide such feedback, the system may be configured such that indicator3426 has a brightness that varies in proportion to the brightness levelof the headlamps. Such variance may be along a continuum or may changein noticeable incremental steps. The brightness of indicator 3426 mayalso be doubled or increased significantly when the headlamps are in ahigh beam state as a result of manual activation of the high beams so asto provide the user with a clear indication that the system hasappropriately responded to such manual activation. Another alternativeindication scheme is to have the indicator change color as a function ofthe brightness of the headlamps. Yet another indication scheme is toconfigure indicator 3426 to include a scale that indicates a relativebrightness of the headlamps. Such a scale may be provided as amulti-segmented display, such as the exemplary display shown in FIG. 38in which the number of segments that are illuminated correspond to therelative brightness of the headlamps. Thus, for example, headlamp iconsegment 3802 may be illuminated at all times that the headlamps are onand the various segments 380-3812 are independently activated with theincreasing brightness level of the headlamps. In addition, the color ofthe indicator shown in FIG. 38 may change to indicate manual activationor operation in either the manual or automatic modes or to indicateoperation of the low beams, DRLs, fog lamps, etc. Another way toindicate to the driver that the headlamp controller is operating in anautomatic control mode is to provide an indicator light in theauto/manual select switch 3415 such that when the user depresses theauto/manual select switch 3415, a light within or near by the switch isactivated. Other indication techniques known in the art may similarly beutilized.

As discussed above, the vehicle headlamps may be operated in asuper-high beam state in accordance with the laws of the variouscountries in which the vehicle may be used. Such super-high beams havebeen proposed to have an intensity of greater than 75,000 cd at 0°vertical and horizontal. Such super-high beams have been approved foruse in Europe and found to be beneficial. In the event the vehicle isequipped with this capability and the appropriate headlights, thecontrol circuit may control the super-high beams to be activated when itdetects that the vehicle is above a predetermined speed level. In thismanner, the super-high beams can most typically only be activated whenthe vehicle is operated on an expressway.

Additionally, if such super-high beams are provided, the system may beprogrammed to have increased sensitivity to light sources detectedforward of the vehicle. The super-high beams may also be faded as lightsources are detected as coming closer to the vehicle.

As shown in FIG. 34, microcontroller 1105 may be coupled to a GPSreceiver 3450 via vehicle bus 3406. Microcontroller 1105 may receiveinformation from GPS receiver 3450 that is indicative of the locationand possibly the direction of travel of the vehicle. GPS receiver 3450may be part of a navigation system or may be part of any other system inthe vehicle. The GPS receiver and antenna may be mounted to the rearviewmirror assembly as disclosed in commonly assigned U.S. Pat. No.6,166,698, the entire disclosure of which is incorporated herein byreference.

The information received from GPS receiver 3450 may be in a form thatalready identifies the location and direction of the vehicle or it maybe in the form of information received directly from the satellites fromwhich the location would need to be computed by microcontroller 1105. IfGPS receiver 3450 is part of a navigation system, the navigation systemmay process the information from the GPS receiver and provide exactlythe information needed by microcontroller 1105. Such information mayinclude, for example, an indication whether or not the road that thevehicle is currently traveling on is a residential road, a dividedhighway, or an expressway. Microcontroller 1105 may then utilize thisinformation to control the exterior lights on the vehicle. Specifically,microcontroller 1105 may prevent actuation of the vehicle high beams orthe super-high beams when the vehicle is traveling on a residentialroad. Microcontroller 1105 may also disable the super-high beams exceptwhen the vehicle is traveling on a divided highway or expressway. Thelocation of the vehicle may also be utilized to automatically enable ordisable the super-high beams based upon a determination of whether thevehicle is located in a country, state, or municipality that permits (orprohibits) the use of such super-high beams. Additionally, the locationof the vehicle may be used to determine whether the vehicle is presentlydriving in a region where vehicles are driven on the left hand side ofthe road or in a region where vehicles are driven on the right hand sideof the road.

LED Headlamps for Headlamp Steering and Headlamp Flashing

It has long been considered to be desirable to provide headlamps thatcan be steered in the direction that the vehicle is turning. It is alsodesirable to provide forward lighting that can be turned OFF, orsubstantially attenuated, for such a short period of time that thedriver does not notice that the lights are OFF. In this way, reflectionsdo not exist during image acquisition. Although a light emitting diode(LED) lamp can be used to provide these features in a cost-effectivemanner, LED lamps producing enough light to implement a vehicle headlampare not commercially available. LEDs suffer from a number ofdisadvantages that limit their application in vehicle headlamps, not theleast of which are the relatively small amounts of light produced byLEDs and manufacturability limitations when incorporating LEDS havingexotic constructions. Because of these disadvantages, LED lamps have notbeen used to implement a vehicle headlamp despite the fact that LEDs aremore rugged, more energy efficient, and significantly longer lastingthan other light technologies. Additionally, means of producing whitelight from LEDS have only recently become practical as discussed in U.S.Pat. No. 5,803,579, entitled ILLUMINATOR ASSEMBLY INCORPORATING LIGHTEMITTING DIODES, issued to John K. Roberts et al. on Sep. 8, 1998, thedisclosure of which is incorporated herein by reference.

An LED headlamp 2600 is disclosed in FIGS. 26 a and 26 b. The LEDheadlamp can be used to very briefly flash OFF, or dim, the headlampsduring an image-sampling interval. The LED headlamp 2600 includes a heatextraction member 2601 that serves as a support for mountingsemiconductor optical radiation emitters 2603, 2605. Where thesemiconductor optical radiation emitters 2603, 2605 are electricallyconnected to the heat extraction member, the heat extraction memberprovides an electrical connection to the semiconductor optical radiationemitters in addition to providing a thermal path for removing heatgenerated within the semiconductor optical radiation emitters duringoperation. It is envisioned that the emitters 2603, 2605 can beelectrically isolated from the heat extraction member such that the heatextraction member only provides a thermal path. Each of the emitters2603 is connected to electrical conductor strip 2607 through a wire bond2609 and a resistor 2611. Each of the emitters 2605 is connected toelectrical conductor strip 2613 through a bonding wire 2615 and aresistor 2617.

The heat extraction member 2601 may be constructed of any suitablematerial, and may be formed in any desired configuration. The front faceof the illustrated heat extraction member is generally rectangular inshape, including 33 wells, each of which receives semiconductor opticalradiation emitters 2603, 2605. The back of the heat extraction memberincludes fins 2621 that provide a large surface for thermal dissipationto the ambient air. It is envisioned that the heat extraction member mayalternatively have other configurations which enable light steering,such as being generally convex, shaped like a portion of a cylinder sidewall, an elongate bar to extend across the front of the vehicle, or aplurality of joined planar surfaces extending at different angles, orthe like. The heat extraction member can be chamfered, or otherwisecontain extensions, slots, holes, grooves and the like, and mayincorporate depressions such as collimating cup or other form to enhanceoptical performance. The illustrated heat extraction member includeselliptical cups 2602. The heat extraction member may be composed ofcopper, copper alloys such as beryllium, aluminum, aluminum alloys,steel, or other metal, or alternatively of another high thermalconductivity material such as ceramic. Preferably, the heat extractionmember is constructed from an electrically and thermally conductivemetal. Such materials are commercially available from a wide variety ofsources.

The cups 2602 are formed in the top surface of the heat extractionmember for receipt of the semiconductor optical radiation emitters. Theillustrated cups 2602 are elliptical to accommodate two emitter chips2603, 2605 side-by-side. However, the cups may be of any suitable shapesuch as round, elliptical, rectangular, square, pentagonal, octagonal,hexagonal, or the like. The elliptical cups have the advantage ofaccommodating more than one emitter while providing an efficientreflector for projecting light outwardly in a desired radiation pattern.It is envisioned that the region of the heat extraction member directlyunderlying the point of attachment of the semiconductor opticalradiation emitter may be coated with nickel, palladium, gold, silver orother material including alloys, in order to enhance the quality andreliability of the die attach. Other thin-layered materials may beoptionally inserted between the emitter and the heat extraction memberto achieve a variety of desired effects without departing from the scopeand spirit of the present invention. The material preferably provides anelectrical connection between the emitters and the heat extractionmember whereby the heat extraction member can provide a referencepotential, which may for example be ground potential. The materials arepreferably adhesive, electrically insulative, and either conductive orpatterned composite of electrically insulative and conductive materials,and without significantly impeding thermal transfer, may be used tosupport, bond, electrically connect or otherwise mount to the emitter tothe heat extraction member. The region of the heat extraction memberwithin optical-enhancement cup feature may be coated with silver,aluminum, gold or other suitable material to increase reflectance andimprove the optical efficiency of the device. The area outside of theencapsulant may be coated with nichrome, black oxide or other highemissivity treatment to improve radiative cooling.

The connection of the semiconductor optical radiation emitter ispreferably by the use of a special type of electrically conductiveadhesive die-attach epoxy. These adhesives normally achieve goodelectrical conductivity by inclusion metallic fillers such as silver inthe adhesive. Suitable die-attach adhesives are well known in the artand may be obtained from Quantum Materials of San Diego, Calif., fromAblestik division of National Starch and Chemical, and EpoTek ofBillerica, Mass. Alternatively, solder may be used as a means ofattaching the LED chip to the heat extraction member in someembodiments. Whether attached by electrically conductive adhesive orsolder, the bond establishes good electrical and thermal conductivitybetween the emitter and the heat extraction member. In the case wherethe emitters having electrodes manifest as conductive bond pads at thetop of the LED chips rather than at their base, the electricalattachment of all of the electrodes is by wire bond rather than by dieattach to the heat extraction member.

The semiconductor optical radiation emitters comprise any component ormaterial that emits electromagnetic radiation having a wavelengthbetween 100 nm and 2000 nm by the physical mechanism ofelectroluminescence, upon passage of electrical current through thematerial or component. For purposes of generating head lightillumination, different emitters can be used in the wells to generatethe light, such as: all amber emitters the wells; or amber and cyanemitters positioned in each of the wells; or red-orange and cyanemitters placed in each of the wells; or cyan and amber emitters placedin some of the wells and red-orange and cyan emitters in other wells;phosphorous emitters in each of the wells; or the like. It is envisionedthat four out of the five wells can have blue-green and amber emittersand one in five wells can have red-orange and amber emitters. Such anarrangement will produce a white light for illuminating the path of thevehicle.

The semiconductor optical emitter may comprise a light emitting diode(LED) chip or die as are well known in the art, light emitting polymers(LEPs), polymer light emitting diodes (PLEDs), organic light emittingdiodes (OLEDs) or the like. Such materials and optoelectronic structuresmade from them are electrically similar to traditional inorganicmaterials known to those skilled in the art, and are available form avariety of different sources. Semiconductor optical radiation emitter,or emitter, as used herein refers to each of these and theirequivalents. Examples of emitters suitable for headlamps include AlGaAs,AlInGaP, GaAs, GaP, InGaN, SiC, and may include emissions enhanced viathe physical mechanism of fluorescence by the use of organic orinorganic dies or phosphors. LED chips suitable for use in the presentinvention are made by companies such as Hewlett-Packard, NichiaChemical, Siemans Optoelectronics, Sharp, Stanley, Toshibe, Lite-On,Cree Research, Toyoda Gosei, Showa Denko, Tyntec, and others. Such chipsare typically fashioned approximately in square base between 0.008″ and0.016″ long on each side, a height of about0.008″ to 0.020″ . Toimplement the headlight, a larger chip having a square base larger than0.020″ may be used, and in particular it is advantageous to have a sizegreater that 0.025″ to 0.035″ to generate light. An array of suchemitters mounted to a substantial heat sink permits an LED lamp togenerate sufficient light to operate as a vehicle headlight. Details ofan emitter that can be used can be found in U.S. patent application Ser.No. 09/426,795, filed on Oct. 22, 1999, entitled SEMICONDUCTOR RADIATIONEMITTER PACKAGE, by John K. Roberts et al., now U.S. Pat. No. 6,335,548,the disclosure of which is incorporated herein by reference. Anelectrical path for supplying control signals to the emitters isprovided through conductors. The conductors are electrical stripsapplied to a surface of an insulative layer. The insulative layer beingmounted to the top surface of the heat sink. The insulative layer may bea circuit board including openings over the cups, or it may comprise anepoxy or plastic layer. The conductor may be any suitable electricallyconductive material such as copper, aluminum, an alloy, or the like, andmay advantageously comprise circuit traces applied to the insulatingmaterial by conventional means. The circuit traces disclosed in FIG. 26a illustrate a pattern that may be used where separate supply isprovided for the different emitters.

An encapsulant is a material or combination of materials that servesprimarily to cover and protect the semiconductor optical radiationemitter and wire bonds. The encapsulant is transparent to wavelengths ofradiation. For purposes of the present invention, a substantiallytransparent encapsulant refers to a material that, in a flat thicknessof 0.5 mm, exhibits greater than 20% total transmittance of light at anywavelength in the visible light range between 380 nm and 800 nm. Theencapsulant material typically includes a clear epoxy or other thermosetmaterial, silicone or acrylate. Alternatively, the encapsulant mayconceivably include glass or thermoplastic such as acrylic,polycarbonate, COC or the like. The encapsulant may include materialsthat are solid, liquid or gel at room temperature. The encapsulant mayinclude transfer molding compounds such as NT 300H, available form NittoDenko, or potting, encapsulation or other materials which start as asingle part or multiple parts and are processed with a high temperaturecure, two part cure, ultra-violet cure, microwave cure, or the like.Suitable clear encapsulants may be obtained from Epoxy Technology ofBillerica, Mass., from Nitto Denko America, Inc., of Fremont, Calif., orfrom Dexter Electronic Materials of Industry, California.

The encapsulant may provide partial optical collimation or other beamformation of electromagnetic energy emitted by the emitter and orreflected by the surface of heat extraction member. The encapsulant alsoserves as a chemical barrier, sealant, and physical shroud providingprotection of emitters, internal adhesives such as bonds, bond pads,conductor wires, wire bonds and internal surfaces of heat extractionmember and electrical leads from environmental damage due to oxygenexposure, exposure to humidity or other corrosive vapors, solventexposure, mechanical abrasion or trauma, and the like. Encapsulantprovides electrical insulation. Encapsulant may also provide forattaching or registering to adjacent components such as secondaryoptics, support members, secondary heat extractors, and the like.

The encapsulant may comprise a heterogeneous mass of more than onematerial, wherein each material occupies a portion of the overallencapsulant volume and provides a specialized function or property. Forexample, a stress relieving gel such as a silicone “glob top” may beplaced over the emitter and wire bonds. Such a localized stressrelieving gel remains soft and deformable and may serve to cushion theemitter and wire bonds from stress incurred during subsequent processingof the component or due to thermal expansion to shock. A hard moldingcompound such as an epoxy, may then be formed over the stress relievinggel to provide structural integration for the various features of thecomponent, to retain the electrical leads, to protect the internalmechanisms of the component from environmental influences, toelectrically insulate the semiconductor radiation emitters, to providevarious optical moderation of radiant energy emitted by the emitter ifdesired.

Additionally, the filler used within the stress relieving gel mayadvantageously include a high thermal conductivity material such asdiamond powder. Diamond is a chemically inert substance with anextremely high thermal conductivity. The presence of such a material maysignificantly increase the thermal conductivity of the gel and providean additional path for heat generated in the emitter chip to reach theheat extraction member and ambient environment where it can bedissipated. Such additional heat extraction path will increase theefficiency of the emitter, and thus the light output of the lamp. Theencapsulant, and manufacture of a device using such an encapsulant isdescribed in greater detail in U.S. Pat. No. 6,335,548, incorporated byreference hereinabove.

A steerable light emitting diode headlamp 2700 is illustrated in FIG.27. The headlamp includes a heat extraction member 2701 having two lampsections 2703 and 2705. The heat extraction member 2701 is configured toinclude the two lamp sections 2703 and 2705 each of which issubstantially identical to lamp 2601, presenting two front faces at anangle of 5° to 45°, and may advantageously be angled at approximately15°.

Another alternative design for a headlamp for providing low and highbeams is illustrated in FIG. 28. The headlamp 2800 includes a heatextraction member 2801 having two lamp sections 2803 and 2805. The heatextraction member 2801 is configured to include the two lamp sections2803 and 2805, each of which is substantially identical to lamp 2601.The heat extraction member provides two front faces at an angle of 1° to2°, and may advantageously be angled at approximately 1.5°. The angle isexaggerated in FIG. 28 so that the angled surfaces are readily visible.

By controlling the selection of the LEDs that are illuminated, theheadlights can be aimed. It is also envisioned that the front of the carcan have LED chips positioned in a bar running across the front grill.

Whereas the above embodiment takes advantage of directly mounting anumber of chips on a common heat sink, it is also envisioned that anarray of discrete LED lamps can be used to implement an LED headlamp2650 (FIGS. 26 c and 26 d). Each discrete LED lamp preferably includes aheat extraction member for dissipating power generated by the emittersto obtain a brighter light level without damaging the LED components. Aparticularly advantageous high power LED lamp which is uniquely adaptedfor conventional manufacturing processes is disclosed in U.S. patentapplication Ser. No. 09/426,795, entitled SEMICONDUCTOR RADIATIONEMITTER PACKAGE, filed on Oct. 22, 1999, by John K. Roberts et al., nowU.S. Pat. No. 6,335,548, the disclosure of which is incorporated hereinby reference. Other LED lamps that could be used are commerciallyavailable from LED manufacturers such as Hewlett Packard Company.

The LED lamps 2650 (only some of which are numbered) are mounted to acircuit board 2652 and heat sink 2654 (FIG. 26 d). The circuit board canprovide a secondary heat sink, where the conductive layer 2660 of thecircuit board exposed to ambient air, by thermally coupling the heatextraction member 2664 of each LED lamp to the conductive layer 2662 ofthe circuit board. The heat extraction member of the LED lamp is alsothermally coupled to the heat sink 2654. In the illustrated embodimentof FIGS. 26 c and 26 d, the thermally conductive material 2670 ispositioned in a hole through the circuit board below the heat extractionmember. The thermally conductive material is thicker than the circuitboard, and resilient. For example, the thermally conductive material canbe provided using a preformed thermal coupler such as a silicon based,cut resistant material commercially available from Bergquist, andidentified as Silipad 600. Packages for LED lamps using the heatextraction member are disclosed in U.S. patent application Ser. No.09/425,792, entitled INDICATORS AND ILLUMINATORS USING A SEMICONDUCTORRADIATION EMITTER, filed on Oct. 22, 1999, by John K. Roberts et al.,now U.S. Pat. No. 6,441,943, the disclosure of which is incorporatedherein by reference thereto.

Where red-green-blue or binary complementary lighting is used, it isenvisioned that only selected chips will be flashed OFF when attemptingto distinguish reflective objects from lamps.

Thus, for binary complementary emitters, only amber emitters need tohave a briefly reduced intensity. Additionally, it will be recognizedthat instead of turning the headlamps OFF, the light level can bereduced to a level at which reflections will be below the pixelthreshold at which the image sensor assembly will detect an object.

Other LED device/component structures that may be employed are disclosedin commonly assigned U.S. Provisional Application No. 60/265,487,entitled HIGH POWER RADIATION EMITTER DEVICE AND HEAT DISSIPATINGPACKAGE FOR ELECTRONIC COMPONENTS, filed on Feb. 1, 2001, by John K.Roberts et al. and in commonly assigned U.S. Provisional Application No.60/265,489, entitled RADIATION EMITTER DEVICES AND METHOD OF MAKING THESAME, filed on Jan. 22, 2001, by John K. Roberts et al.

Surface Mounted Filter for Sensor

A method by which a filter can be directly deposited onto asemiconductor light sensor 201 will now be described with respect toFIGS. 29 a through 29 d. In the first step, a photoresist 2877 isdeposited over the entire wafer 2972. The photoresist may be anysuitable commercially available photoresist material. Portions of thephotoresist may be removed such that the remaining photoresist 2877 ispatterned to cover only those areas on the surface of the waferrequiring protection from the optical coating deposition, such as thebonding pad 2975, as shown in FIG. 29 b. The optical film coating 2979is then applied to the surface of the die 2972 as shown in FIG. 29 c.

The thin film 2979 is deposited directly on the light sensor 2932 inmultiple layers. The red and cyan filters, if red and cyan filters aredesired, will be applied separately. An example of a cyan filter will benow be described. To make a cyan filter, the layers of titanium dioxide(TiO₂) and silicon dioxide (SiO₂) described in Table 1 can be used. Tomake a red filter, the layers described in Table 2 can be used. Thelayer number is the order in which the material is applied to the wafersurface.

TABLE 1 Layer Material Thickness (nm) 1 SiO₂ 170 2 TiO₂ 124 3 SiO₂ 10 4TiO₂ 134 5 SiO₂ 160 6 TiO₂ 79 7 SiO₂ 164 8 TiO₂ 29 9 SiO₂ 168 10 TiO₂ 6811 SiO₂ 164 12 TiO₂ 33 13 SiO₂ 163 14 TiO₂ 69 15 SiO₂ 154 16 TiO₂ 188 17SiO₂ 148 18 TiO₂ 88 19 SiO₂ 319

TABLE 2 Layer Material Thickness (nm) 1 TiO₂ 68 2 SiO₂ 64 3 TiO₂ 35 4SiO₂ 138 5 TiO₂ 57 6 SiO₂ 86 7 TiO₂ 50 8 SiO₂ 78 9 TiO₂ 73 10 SiO₂ 94 11TiO₂ 54 12 SiO₂ 89 13 TiO₂ 52 14 SiO₂ 87 15 TiO₂ 50 16 SiO₂ 74 17 TiO₂28 18 SiO₂ 61 19 TiO₂ 49 20 SiO₂ 83 21 TiO₂ 48 22 SiO₂ 78 23 TiO₂ 48 24SiO₂ 91

After all of the layers are deposited, the photoresist is lifted offusing a conventional lift off process, leaving the film deposited overthe light sensitive region, but not over the bonding pads, as shown inFIG. 29 d. The resulting die can be encapsulated to provide the imagearray sensor in conventional packaging.

The characteristics of the filters produced according to Table 1 andTable 2 are illustrated in FIGS. 30 and 31. In particular, the redfilter will attenuate light below 625 nm whereas the blue filter willpass light between approximately 400 nm and 625 nm. Both filters willpass light above 800 nm. An infrared filter can be utilized to reducethe effect of infrared light on the performance of the headlight dimmer.

Those skilled in the art will recognize that the filters describedherein are exemplary, and other filters, materials, or materialthickness could be used to implement the filter function. Othermaterials could be applied in a similar manner to provide these or otherfilter characteristics.

Those skilled in the art will also recognize that the layer thicknessesare rounded to the nearest nanometer. Although there will be sometolerance permitted, good precision in the stack construction isrequired. It will also be recognized that the layer thicknesses areexemplary. By surface mounting the filters, the cost of providing theimage sensor can be greatly reduced, as components and manufacturingcomplexity are reduced. Additionally, an infrared filter can be appliedas a coating between the pixels and the red and blue filters.

Package

An alternate optical sensor assembly 3200 is disclosed in FIG. 32.Optical sensor assembly 3200 includes a base substrate 3202, which istransparent. The substrate may be manufactured of any suitable materialsuch as a transparent polymer, glass, or the like. Alternately, it isenvisioned that the base substrate may be manufactured of a commerciallyavailable infrared interference filter such as those describedhereinabove. Alternatively, a thin film filter may be attached to atransparent glass element to make the base substrate 3202.

The lower surface of the base substrate has conductive strips 3210 forconnection to the image array sensor 3212. The base substrate ispreferably an electrical insulator, whereby the strips can be anysuitable electrically conductive material applied directly to the lowersurface of the base substrate by conventional manufacturing processes.Alternatively, if the base substrate is an electrical conductor, thestrips can be applied to an electrical insulator, which is in turnapplied to the base substrate.

The image array sensor 3212 is flip chip bonded to the lower surface ofthe base substrate 3202 by soldering pads 3211. A dielectric material3214, such as an epoxy, encloses the image array sensor. The dielectricmaterial preferably bonds with the conductive strips 3210 and thetransparent element 3202. Clips 3204 and 3206 clip onto the edges of thebase substrate and make electrical contact with respective conductivestrips 3210. A respective clip can be provided for each of theconductive strips 3210. Leads 3213, 3215 extend from the clips forinsertion into support substrate 3201, which can be a printed circuitboard, a housing, or the like. The support substrate is preferably aprinted circuit board carried in a housing, such as a rearview mirrormount housing. The stops 3205, 3207 limit the length of the leads thatcan be inserted into the support substrate. Alternatively, the clips canbe configured for surface mounting. Examples of surface mountable clipsinclude NAS Interplex Edge Clips, from NAS Interplex, an InterplexIndustries Company located in Flushing, N.Y., USA.

Packages for mounting the image array sensor are described in U.S. Pat.No. 6,130,448, OPTICAL SENSOR PACKAGE AND METHOD OF MAKING THE SAME,filed on Aug. 21, 1998, by Fred Bauer et al., the disclosure of which isincorporated herein by reference.

The assembly of the lens to the base substrate can be provided in thesame manner as described hereinabove. In particular, the lens structureis carried on the base substrate 3202. The lens structure can beidentical to the lens structure 202, and thus can be half clear and halfred, or half cyan and half red, or entirely clear where a color filteris applied directly to the surface of the image sensor as describedabove with respect to FIGS. 29 a-29 d. To make the lens assembly, atransparent member and a UV curable adhesive can be used. Thetransparent member can be an epoxy member like members 230, 802. The UVcurable adhesive can be identical to adhesive 232.

Radar

A wave transceiver 101 (FIG. 1) can be used to acquire additionalintelligence usable for controlling the operation of the controlledvehicle 100. The wave transceiver can be used without the image arraysensor 102, or it can be used with the image array sensor. The wavetransceiver device 101 is mounted on a vehicle 100 and oriented in agenerally forward direction. The wave transceiver device 101 ispositioned to receive the reflections of waves emitted by thetransceiver device after they have reflected off objects in front of thevehicle 100. The wave-emitting device may be a radar system operating,for example, in a frequency range exceeding 1 GHz (77 GHz is designatedfor vehicular radar in many European countries) or an optical radarutilizing, for example, laser diodes for the wave-emitting device.Alternatively, the wave-emitting device 101 may be an ultrasonictransducer emitting ultrasonic waves. The wave-emitting device may bescanned across the forward field to cover various angles. For thepurposes of this invention, the term “radar” will be used to encompassall of these concepts. The wave transceiver should not be interpreted asbeing limited to any specific type or configuration of wave transmittingor wave receiving device. The transmitter and receiver may each bemounted within a different respective housing or they both may bemounted in a common housing.

A radar processing system 3300 (FIG. 33) controls the wave transmittingsection 3301, 3302 and interprets the signal received by the wavereceiving section 3304, 3305 to determine the presence of objects aswell as the speed and direction of such objects. A headlamp controller3303 receives target information from the radar processing system, andmay optionally also receive signals from the vehicle speed sensor (suchas a speedometer) and a vehicle direction sensor (such as a compass) andgenerates a control signal which determines the state of the vehicleheadlamps 111. The communication between the radar processing system,the vehicle speed sensor, the vehicle direction system and the vehicleheadlamps may be by one of many mechanisms including direct wiringthrough a wiring harness or by a vehicle communication bus such as theCAN bus. Additionally, systems such as the radar processing system andthe headlamp controller may be implemented by a single integratedprocessor, multiple processors, digital signal processors,microcontrollers, microprocessors, programmable logic units, orcombinations thereof.

More particularly, the system contains a radar system that includes awave transmitting section and a wave receiving section. The wavetransceiver 101 includes an emitter 3301 and a receiver 3304. Thetransmitter may be implemented using an antenna for a conventionalradar, a light source for optical radar, an ultrasonic emitter, anantenna system for a Doppler radar system, or the like. The receiver3304 may be implemented using an antenna in a conventional radar system,a light receiving element in an optical radar system, an ultrasonicreceiver, a wave guide antenna in a Doppler radar system, or the like. Adriver 3302 is connected to the emitter 3301 to condition signals fromcontroller 3303 so that emitter 3301 produces signals, which, whenreflected, can be detected by the receiver 3304. The driver 3302 may beimplemented using a pulse modulator, a pulse shaper, or the like. Thereceiver 3304 is connected to a conditioning circuit 3305 whichconditions the signals detected by the receiver for further processingby controller 3303. The conditioning cirucit may include a demodulator,a filter, an amplifier, an analog-to-digital converter (ADC),combinations thereof, and the like. The controller 3303 may beimplemented using a microprocessor, a digital signal processor, amicrocontroller, a programmable logic unit, combinations thereof, or thelike.

The operation of radars to determine the presence of objects relative toa vehicle are well known, and will not be described in greater detailhereinbelow. For example, the time between the transmitted wave and thedetection of the reflected wave may be used to determine the distance ofan object. The movement of an object over successivetransmission/reception cycles may be used to determine an object'srelative speed and direction. Doppler radar may also be used todetermine the objects speed. The magnitude of the reflected wave may beused to determine the size or density of the detected object. Operationof radars is well known, and will not be described in greater detailherein.

In order to properly control the high beam state of the controlledvehicle 100 it is necessary to determine if an object detected by theradar is a vehicle or a stationary object and, if a vehicle, whether thevehicle is an oncoming vehicle 105 or preceding vehicle 110. This can beaccomplished by comparing the speed and direction of the object with thespeed and direction of the controlled vehicle 100. The speed anddirection of travel of the object is obtained using the radar principlesdescribed above. The speed of the controlled vehicle 100 may be obtainedfrom a speed sensor on the vehicle, a global positioning system (GPS)system, or the like. The direction of the control vehicle 100 may beobtained from a compass sensor, a steering wheel turn indicator, a GPS,or the like.

Once this information is obtained, a simple set of criteria is appliedto determine if the object is a vehicle or a stationary object. If anobject is stationary, it will be moving in a direction opposite thecontrolled vehicle 100 at the same speed as the controlled vehicle. Ifan object is an oncoming vehicle 105, it will be traveling in adirection approximately opposite the controlled vehicle 100 at a speedsubstantially faster than that of the controlled vehicle. Finally, if anobject is not moving relative to the controlled vehicle or the object ismoving at a rate substantially slower than the controlled vehicle, theobject is likely a preceding vehicle 110. The distance at which the highbeams are dimmed may be a function of the speed of the controlledvehicle and may be a function of the angle between an axis straightforward of the controlled vehicle 100 and the oncoming vehicle 105 orpreceding vehicle 110.

In a more advanced system the headlamp control system not only controlsthe high/low beam state of the headlamps 3311, 3312 and high beam lamps3314, 3315 based on the presence of one or more vehicles, but may varythe brightness of the high beam headlamps and low beam headlamps toprovide a continuous transition between the two beams as a function ofthe distance to the nearest other vehicle, thus maximizing the availableluminance provided to the driver of the controlled vehicle withoutdistraction to the other driver. A continuously variable headlamp systemis disclosed in U.S. Pat. No. 6,049,171 entitled CONTINUOUSLY VARIABLEHEADLAMP CONTROL, filed on Sep. 18, 1998, by Joseph S. Stam et al., thedisclosure of which is incorporated herein by reference. The system mayalso vary the aim of the controlled vehicle headlamps in the verticaldirection. The system may be configured to transition between more thantwo beams or may be configured to perform a combination of aiming andvarying the brightness or one or more lamps. The headlamp processingsystem may also use the vehicle direction input to determine the properhorizontal aim of the headlamps to provide better illumination whentraveling on curves. An LED headlamp that facilitates aiming isdescribed above.

A light sensor 3320 can be used to detect ambient light levels and mayoptionally provide other light conditions. The light sensor may beimplemented using a non-imaging sensor such as a silicon photodiode, aparticularly advantageous photodiode disclosed in U.S. patentapplication Ser. No. 09/237,107, entitled PHOTODIODE LIGHT SENSOR, filedby Robert Nixon et al., now abandoned, the disclosure of which isincorporated herein by reference, although other non-imaging photocellscould be used such as cadmium sulphide (CdS) cells, or the like. Thelight sensor 3320 can be alternately be implemented using an opticalimage sensor 102 in addition to, or instead of, a non-imaging lightsensor.

The optical system may contain filters to determine the color of a lightsource. The combination of an optical system with a radar system maybetter overcome the limitations present if only one or the systems areused independently. For example, if a radar system is used independentlyof an imaging system, an oncoming or preceding vehicle waiting at anintersection would be perceived by the radar system as a stationaryobject. However, by combining an optical sensor with the radar system,the lights on the waiting vehicle would indicate that a vehicle ispresent and the radar can determine the actual distance to the vehicle.In general, if an optical system is used, the optical system may be usedto determine the presence of oncoming or preceding vehicles and theradar system may be used to determine the actual distance to suchoncoming or preceding vehicle as well as the speed of that vehicle. Inthis manner, the radar detector and the imaging sensor can be used toverify the presence of other objects. Additionally, the light sensorscan be used to determine light conditions, such as ambient light levels.

The presence of the radar system on the vehicle may enable otherfeatures other than headlamp control to be implemented utilizing thesame components as the headlamp radar, thus reducing the cost of the twosystems combined. Such system may include, for example, adaptive cruisecontrol, obstacle warning systems, collision avoidance systems,autonomous driving systems, or the like. In this case, the wavetransmitting section, wave receiving section, and radar processingsystems could be shared by all features while each feature has its ownprocessing system for determining a course of action based upon theinformation received from the radar processing system. It is alsopossible to integrate the processing systems from each feature into asingle processor.

A radar system is described in U.S. patent application Ser. No.09/531,211, entitled AUTOMATIC HEADLAMP CONTROL SYSTEM, now U.S. Pat.No. 6,403,942, the disclosure of which is incorporated herein byreference.

Mirror Mount Accessory Housing

A preferred mounting structure for mounting the headlamp dimmer systemof the present invention is shown in FIGS. 41-49. As illustrated, thisstructure includes a mount 4101 having a slot 4103 for receiving amounting puck (not shown) that is adhesively secured to the vehiclewindshield. An aperture 4105 is formed in mount 4101 and opens into slot4103 to allow a mount screw 4107 to extend through aperture 4105 andengage a surface of the mounting puck so as to securely hold mount 4101on the puck and thus on the vehicle windshield. Mount 4101 includes aball 4109 to which the socket of a mirror mounting stem (not shown) maybe secured in conventional fashion. The mounting stem may be secured toa similar ball extending from the rearview mirror housing or the stemmay include a ball for engaging a socket formed in the mirror housingbody.

As described in more detail below, a mirror mount accessory housing 4111is secured to mount 4101 and includes a housing cover 4113 consisting ofa right half portion 4113 a and a left half portion 4113 b. As bestshown in FIG. 44, mount 4101 includes a plurality of laterally extendingpegs 4115, which are inserted in corresponding holes 4117 provided inhousing cover portions 4113 a and 4113 b. Additionally, housing coverportions 4113 a and 4113 b include resilient tabs 4119, which extendthrough a pair of slots 4121 on mount 4101 to securely hold housingcover 4113 on mount 4101. Housing cover portions 4113 a and 4113 bfurther include a plurality of tabs 4123 and a plurality of slottedtongues 4125, which snap together to thereby hold together portions 4113a and 4113 b. Housing portion 4113 a includes a forward facing aperture4127 in which a glass filter 4129 may be mounted. As explained furtherbelow, aperture 4127 and glass filter 4129 provide a window throughwhich the inventive camera senses images.

The inventive mirror mount accessory housing structure further includesa baffle/printed circuit board (PCB) holder 4130 (also generallyreferred to herein as a support structure) that is adjustably mounted tomirror mount 4101 and contained within housing cover 4113. As shown inFIG. 44, baffle/PCB holder 4130 includes a pair of slots 4133 forengaging laterally extending pins 4135 on mirror mount 4101. Baffle/PCBholder 4130 further includes a pair of elongated slots 4137 throughwhich screws 4139 are inserted. Screws 4139 extend through slots 4137and are threadably engaged in holes 4141 provided in mount 4101. Byproviding slots 4137 as elongated apertures, the tilt of baffle/PCBholder 4130 may be selectively adjusted relative to mount 4101. Suchtilt adjustability is desirable given the variance of the slope ofvehicle windshields from one model to another. As discussed furtherbelow, the image sensor and its associated circuit board is securelymounted to baffle/PCB holder 4130, and thus, the image sensor tiltrelative to the vehicle windshield may be adjusted by adjusting the tiltof baffle/PCB holder 4130.

As illustrated in FIG. 44, baffle/PCB holder 4130 includes a baffle 4143similar to the baffle discussed above. A forward end of baffle 4143 ispositioned proximate aperture 4127 and glass filter 4129 while an imagesensor 4145, which includes image chip 201, encapsulation block 230, UVcure epoxy 232, lens 202, and an aperture stop 203, as shown in FIG. 2a), extends into the opposite and rearward end of baffle 4143. Imagesensor 4145 is mounted on a PCB 4147 having a connector 4149 mountedthereon. Also mounted on PCB 4147 is an image sensing die (not shown),which functions as a sky sensor in the manner discussed above. Toprovide light from a skyward view relative to the vehicle, a light pipe4151 is mounted over the die on PCB 4147 within a light pipe mount 4153,which engages a corresponding light pipe support 4155 on baffle/PCBholder 4130. Light pipe 4151 includes a pair of laterally extendingprotrusions 4157 that engage corresponding apertures 4159 in a lightpipe filler 4161, which has an aperture 4163 through which the distalend of light pipe 4151 extends. Light pipe filler 4161 is mounted withinan aperture 4165 formed in an upper surface of housing cover 4113. Aswill be apparent to those skilled in the art, light pipe 4151 capturesthe skyward light in its distal end that extends through filler 4161towards the sky, and the skyward light is then directed through lightpipe 4151 to the die on PCB 4147.

As discussed above, a processor may be mounted on PCB 4147 to preprocesssome of the image data obtained from image sensor 4145.

A compass PCB 4171 may optionally be mounted within the inventivehousing structure 4111. Compass PCB 4171 includes a pair of compasssensors 4173, which may be magneto resistive sensors, magneto inductivesensors, flux-gate sensors, or the like. By mounting compass PCB 4171 onbaffle/PCB holder 4130, the relative tilt of sensors 4173 may beadjusted relative to the vehicle horizontal to ensure accurate sensing.Compass PCB 4171 includes a connector (not shown) to which acorresponding connector 4175 may be coupled. Connector 4175 connectscompass PCB 4171 to a processor (not shown) in the mirror body via cable4177. Cable 4177 also connects the same or a different processor withinmirror body to PCB 4147 via a coupler 4179 and coupler 4149. A pair ofresilient prongs 4181 of a clip structure 4183 is disposed behind PCB4147 and secures to baffle/PCB holder 4130. Baffle/PCB holder 4130includes a lateral extension 4187, which extends around connectors 4149and 4179 and provides a ledge upon which resilient prongs 4181 may latchto secure the clip 4183 and PCB 4147 to baffle/PCB holder 4130 and toassist in securing the engagement of couplers 4149 and 4179.

The above-described mounting structure provides several advantageousfeatures. Specifically, the tilt angle of the image sensor may beselectively adjusted while not requiring movement of the housing coverrelative to the mirror mount. This avoids the need to have mountingscrews accessible from the exterior of the housing and thus reduces thepossibility of someone tampering with the adjustment subsequent to finaladjustment by the manufacturer. Further, the interior components shownin FIGS. 46-49 may be secured to mirror mount 4101 after it has beensecured to the vehicle windshield and the adjustment may then be madewith the housing cover subsequently snapped into place following finaladjustment.

An additional advantage is provided by the use of light pipe 4151. Inthe absence of light pipe 4151, an additional circuit board would needto be mounted at an angle relative to PCB 4147 to aim the die mounted onsuch an inclined PCB towards the sky above the vehicle.

Although the mirror mount accessory housing has been described formounting an image sensor, sky sensor, and compass sensors, it will beappreciated that any one or combination of these components may bedisposed in the housing. Further, other components may be disposed inthe housing in addition to, or in place of, any or all of the abovecomponents.

While the present invention has generally be described as preferablyutilizing the full capability of the exterior lights to produce a largenumber of potential beam patterns that may change discretely or througha continuum, it is possible to use the system to simply turn headlampson and off, as disclosed, for example, in U.S. patent application Ser.No. 09/491,192, entitled VEHICLE EQUIPMENT CONTROL WITH SEMICONDUCTORLIGHT SENSORS, filed by Jon Bechtel et al. on Jan. 25, 2000, now U.S.Pat. No. 6,379,013, the disclosure of which is incorporated herein byreference.

While the invention has been described in detail herein in accordancewith certain embodiments thereof, many modifications and changes may beeffected by those skilled in the art without departing from the spiritof the invention. Accordingly, it is intended that the appended claimsnot be limited by way of details and instrumentalities describing theembodiments shown herein.

1. A vehicle imager assembly, comprising: an image sensor having anarray of pixels and at least one other component; and an optical baffledisposed between said image sensor and a scene to be imaged forpreventing light from the scene from reaching said at least one othercomponent.
 2. The imager assembly of claim 1 wherein said image sensoris a CMOS sensor.
 3. The imager assembly of claim 1 wherein said imagesensor is disposed in a rearview mirror assembly.
 4. The imager assemblyof claim 1 further comprising a vehicle mounting structure configuredfor mounting in a fixed position.
 5. The imager assembly of claim 4further comprising a support structure, said image sensor is carried bysaid support structure to allow positional adjustment of said imagesensor relative to a scene and independent of a rearview mirror.
 6. Theimager assembly of claim 5 further comprising a housing secured to saidmounting structure, said support structure and said image sensor beingdisposed in said housing.
 7. The imager assembly of claim 6 wherein bothsaid housing and said support structure are attached to said mountingstructure such that positional adjustment of said image sensor may beperformed without changing the position of said housing relative to saidmounting structure.
 8. A vehicle imager assembly, comprising: a vehiclemounting structure configured for mounting in a fixed position; an imagesensor; and a support structure, said image sensor carried by saidsupport structure, said support structure being attached to saidmounting structure to allow positional adjustment of said image sensorrelative to a scene and independent of a rearview mirror.
 9. The imagerassembly of claim 8 and further comprising a housing secured to saidmounting structure, said support structure and said image sensor beingdisposed in said housing.
 10. The imager assembly of claim 9 whereinboth said housing and said support structure are attached to saidmounting structure such that positional adjustment of said image sensormay be performed without changing the position of said housing relativeto said mounting structure.
 11. The imager assembly of claim 9 furthercomprising a light sensor.
 12. The imager assembly of claim 11 furthercomprising a light pipe extending from said light sensor to an apertureformed in said housing that is directed upward towards the portion ofthe sky from which light is to be sensed.
 13. The imager assembly ofclaim 8, wherein said mounting structure is a rearview mirror assemblymounting structure.
 14. The imager assembly of claim 13 wherein saidrearview mirror assembly mounting structure is configured for securing arearview mirror assembly to a vehicle windshield.
 15. A sky sensorassembly for sensing light in the sky above a vehicle, said assemblycomprising: a housing configured for mounting to the vehicle; an imagesensor disposed within said housing; a light pipe extending from saidimage sensor to an aperture formed in said housing that is directedupward towards the portion of the sky from which light is to be sensed.16. The sky sensor assembly of claim 15 wherein said housing is acomponent of a rearview mirror assembly.
 17. The sky sensor assembly ofclaim 16 wherein said housing is an accessory housing mounted to amounting structure for a rearview mirror assembly.
 18. The sky sensorassembly of claim 15 further comprising a circuit board that is disposedvertically within said housing, wherein said image sensor is mounted tosaid circuit board.
 19. The sky sensor assembly of claim 18 where insaid image sensor is mounted to said circuit board for sensing imagesforward of the vehicle.
 20. The sky sensor assembly of claim 15 whereinsaid image sensor is carried by a support structure and a mountingstructure, wherein both said housing and said support structure areattached to said mounting structure such that positional adjustment ofsaid support structure may be performed without changing the position ofsaid housing relative to said mounting structure.